Understanding ocean chemistry in the Western Interior Seaway during the Cenomanian–Turonian Extinction Event.

The boundary between the Cenomanian and Turonian stages of the Cretaceous Period is marked by a mass extinction event that saw the demise of a quarter of the marine invertebrates present at the onset of the crisis, combined with carbon, oxygen, and sulphur isotope levels, the deposition of a thick (up to 3 m in places), organic-rich, black shale in many ocean basins, and the onset of a greenhouse climate, known as the Cretaceous Climatic Maximum, which peaked in the early Turonian, then gradually cooled off over the remaining 24 million years of the Cretaceous. Numerous causes have been proposed for the Cenomanian–Turonian Extinction, but the most likely is thought to be massive volcanic emplacements, possibly in the Caribbean Large Igneous Province, which injected large amounts of carbon dioxide, hydrogen sulphide, and sulphur dioxide, as well as a variety of metal compounds, into the ocean-atmosphere system. Increasing atmospheric carbon dioxide would have led to higher global temperatures and higher precipitation on land, which in turn would have led to higher erosion on land, more nutrients being washed into the oceans, and vast Algal Blooms, which would be recorded as a higher burial rate for organic carbon, causing the global carbon isotope excursion, which can be observed from both black shales and carbonate rocks spanning the Cenomanian–Turonian boundary. At the time much of the world's ocean system was dominated by shallow, epicontinental seas (i.e. seaways covering continents in the already warm Cretaceous world), which would have quickly become stagnant when these Algal Blooms were combined with a combination of an injection of oxygen consuming metals and a break-down in ocean circulation caused by the rising temperatures, resulting in large portions of the global ocean becoming anoxic and hostile to multicellular life. The widespread occurrence of black shales at the Cenomanian–Turonian boundary is thought to be a reflection of this. Curiously, however, these phenomena are not recorded in all sequences spanning the Cenomanian–Turonian boundary, with many shallow marine environments (which would be predicted to be the most severely impacted by such events) seemingly unaffected. This variability, with the event leaving a strong signal in some sequences, a light one in others, and being totally absent in some places, leads to the conclusion that the 'global event' may in fact have been a series of overlapping local occurrences, driven by multiple factors rather than a single change in global atmospheric composition.

In a paper published in the journal Scientific Reports on 30 June 2021, Rob Forkner of the Deep Time Institute, Jeremy Dahl of Biomarker Technologies, Inc., and the Stanford University Institute for Materials and Energy Sciences, Andrea Fildani, also of the Deep Time Institute, Silvana Barbanti, also of Biomarker Technologies, Inc., Inessa Yurchenko of the Department of Geological Sciences at Stanford University, and Mike Moldowan, again of the Deep Time Institute, present the results of a study of the USGS Portland-1 core, which was drilled in Colorado, and which includes a section of the Greenhorn Formation including the Cenomanian–Turonian boundary.

 

Palaeogeographic map of North America during Oceanic Anoxic Event 2. The location of the Portland-1 core as well as active volcanic centres are shown. Forkner et al. (2021).

Forkner et al. sampled the core through the Cenomanian–Turonian boundary interval (as determined by the isotope excursion), as well as on either side, for organic geochemical analyses. They initially targeted layers with high organic carbon which were thick enough to determine if reworking or bioturbation had occurred, although this severely limited the number of suitable layers, with the effect that samples were taken at intervals of between 3 and 12 cm across the boundary interval, and 20 cm or more outside this interval. The samples were round segments 2-3 cm in diameter and 1 cm thick taken from the larger core, which were first tested for rock richness and maturity (the extent to which rocks have been heated, altering organic molecules preserved within them), before the most suitable samples were selected for analysis by gas chromatography–mass spectrometry.

Molecular fossils, or biomarkers, are recognisable fragments of molecules synthesised by biological organisms, which can be used to determine the presence and abundance of groups of organisms. Forkner et al. analysed biomarkers from the Portland-1 core across the Cenomanian–Turonian boundary, thereby obtaining a series of snapshots of the water column ecology, which were used to develop a new molecular stratigraphy for the boundary, thereby deriving a wealth of new information with regard to the biota, depositional environment, and the multiple drastic environmental changes that occurred before, during, and after the Cenomanian–Turonian Extinction Event.

A geological examination was used to establish a lithological sequence of events (i.e. changes in the rock type being laid down over time, which would have related to local environmental conditions), using photographs to cover those sections of the core which have previously been heavily sampled by previous workers. This enabled the comparison of similar facies ( specified characteristics, which can be any observable attribute of rocks), in order to correlate changes in the biota in intervals with similar climatic and environmental conditions. This selection process meant that effectively only the finest grained, dark mudrocks were sampled, as these gave the greatest opportunity to detect changes in the water column biota uninfluenced by sedimentary conditions.

The data obtained from the Portland-1 core indicates that, in this area of the Cretaceous Western Interior Seaway at least, conditions in the water column during the Cenomanian–Turonian boundary event (sometimes known as the Cenomanian–Turonian Ocean Anoxic Event) conditions do not appear to have been particularly anoxic. In fact, the sediments laid down across the boundary appear to have been laid down in a more oxygenated environment than wither the sediments above the boundary or those below it, something which has been noted at other locations in the Western Interior Seaway, and coeval shallow water deposits from the Tethys Ocean. The sediments laid down before the boundary layers are predomanenty finely laminated, whereas those across the boundary interval are mostly heavily bioturbated, suggesting a thriving benthic community living within them.

 

USGS Portland-1 core lithologic section, carbon isotope profile and RockEval data. Facies Explanation: (1) Peloidal/foraminiferal, packstone/grainstone; (2) Bioturbated peloidal packstone; (3) Bioturbated peloidal wackestone; (4) Skeletal grainstone; (5) Rippled mudstone; (6) Silty laminated mudstone; (7) Diffusely laminated mudstone; (8) Massive mudstone; (9) Bentonite. Samples were limited to facies (7) and (8). The occurrence of bioturbated peloidal carbonates during the Oceanic Anoxic Event positive carbon isotope excursion indicates that the environment at the time of deposition was oxygenated and supported a diversity of tropical marine life. Note that the core is measured in imperial units as the Portland-1 core and core photos are curated with imperial measurements. This reference is preserved here in the case that the reader wishes to cross-reference these results to the Portland-1 core. Radio-isotopic measurements from bentonites A, B, and C, along with biostratigraphy and correlation of depositional cycles to orbital timescales have produced an average sedimentation rate of 0.93 cm/per thousand years during the Oceanic Anoxic Event positive carbon isotope excursion. The interval of samples with the greatest flux in measured biomarker concentration occurs from about 473 feet (144 m) to about 479 feet (146 m), in the central portion of the Oceanic Anoxic Event positive carbon isotope excursion. Sample spacing in this interval is somewhat irregular in order to stay within the same depositional facies, but varies between 3 and 12 cm indicating that rapid flux in organic geochemical composition of analysed sediments over periods approximately 3–15 thousand years. The carbon isotopic excursion (CIE) that defines the Oceanic Anoxic Event is shown on the carbon¹³ as a proportion of total carbon (δ¹³C) track and highlighted in blue on all compound tracks. Hydrogen Index (HI) is generally negatively correlated with depositional environment oxygen concentrations, thus supporting the trend of Oceanic Anoxic Event positive carbon isotope excursion oxygenation. Oxygen Index (OI) generally correlates positively with depositional environment oxygen concentrations, and again provides evidence for oxygenation during the Oceanic Anoxic Event positive carbon isotope excursion. Forkner et al. (2021).

The geochemical analysis of samples extracted from the core supports the geological analysis. The 'Hydrogen Index', which derives from the proportion of total organic carbon made up of hydrocarbons, is generally negatively correlated with the oxygen concentration in the depositional environment, i.e. the Hydrogen Index tends to go up when there is less oxygen and down when there is more oxygen. In the Portland-1 core the Hydrogen Index above the Cenomanian–Turonian boundary layer averages at 509, during the boundary the average fell to 177, and below the boundary the average rose again, to 423, supporting the idea that oxygen levels in the water column rose rather than fell during the boundary interval. The 'Oxygen Index', derived from the purporting of carbon dioxide to total organic carbon, is positively correlated with the level of oxygen in depositional environment (i.e. the Oxygen Index goes up when the amount of oxygen present in the depositional environment goes up). In the Portland-1 core the Oxygen Index above the boundary layer averages 16, in the boundary layer averages 28, and below the boundary layer averages 15, again suggesting a rise in oxygen levels across the boundary interval.

A number of biomarkers also strongly imply a rise in oxygen levels during the Cenomanian–Turonian boundary interval. The Gammacerane Index is derived from the ratio of the biomarker gammacerane (derived from bacterivorous Ciliates) to hopane (derived from Bacteria), is associated with stratification in the water column, with high levels of gammacerane typically indicating highly saline or reducing conditions. In the Portland-1 core the Gammacerane Index drops to its lowest level during the Cenomanian–Turonian boundary interval, implying conditions became less reducing (generally a sign of higher oxygen levels). The Homohopane Index is derived from the proportion of C₃₅ hopanes (hopane molecules with 35 carbon atoms) to the total C₃₁-C₃₅ hopanes (hopanes with between 31 and 35 carbon atoms). This idex also tends to rise with reducing conditions, and again has its lowest valuse in the Cenomanian–Turonian boundary interval in the Portland-1 core, again suggesting that the enviroment became less reducing during this interval. The proportions of A-oleanane relative to oleanane and 17α-diahopane relative to 17α-hopane are also thought to be indicative of higher oxygen levels, since both A-oleanane and 17a-diahopane require oxygen for their producers (Bacteria and Flowering Plants, respectively), to form them from their precursors, oleanene and hopane. The levels of A-oleanane and 17a-diahopane remain constant throughout the section, but the levels of oleanene and hopane fall during the Cenomanian–Turonian boundary layers, so that the proportion of A-oleanane and 17a-diahopane rise, presumably indicative of a rise in oxygen. 

 

Compound tracks through the Cenomanian–Turonian boundary layers relating to oxygenation before, during, and after the event. Gammacerane and Homohopane Indexes, which are affected by sediment redox conditions, show a significant decrease and the ratios related to 17α-Diahopane exhibit an increase with striking fluctuations within the Cenomanian–Turonian boundary layers. These broad scale changes reflect an overall increase in oxygenation during the Cenomanian–Turonian boundary interval, with periods of reducing conditions punctuated through the event. The relative preservation of des-A-oleanane revealed by the des-Aoleanane/oleanane ratio could be a function of oxidation. Forkner et al. (2021).

Given the generally healthy ecosystem recorded in the sediments of the Portland-1 core across the Cenomanian–Turonian boundary, and the geochemical evidence for a healthy, well-oxygenated water column, biomarkers associated with primary Algal production would be expected to increase across the Cenomanian–Turonian boundary layer. However, a range of such biomarkers, including cholestanes, ergosteranes and C₂₇, C₂₈, and C₃₀ steranes, undergo fluctuations in the boundary layer, with a general decrease in levels. This would appear to represent a deteriorating environment, with repeated stressful intervals.

While this decrease in steranes implies a drop in Algal productivity across the Cenomanian–Turonian boundary, levels of hopanes, indicative of Bacterial productivity, remain relatively high, although again they undergo some severe fluctuations during the boundary interval, suggesting that environmental conditions were fluctuating in the water column. 

Fluctuating biomarker ratios are highly indicative of an unstable environment, with fluctuating primary productivity. In order to further explore this, Forkner et al. examined three further examples. The hopane/sterane ratio reflects the levels of both heterotrophic and photosynthetic Bacteria to primary producers including marine Algae and terrestrial Plants. The 3β-methylhopane/dinosteranes ratio compares the ratio of 3β-methylhopane, derived from aerobic methanotrophs and fermentative Bacteria, to the ratio of dinosteranes, which are almost exclusively derived from Dinoflagellates. The 3β-methyl-24-ethylcholestane/4α-methyl-24-ethylcholestane ratio compares a reworked sterane to one produced by marine Algae. All of these ratios record a significant drop in primary production across the Cenomanian–Turonian interval, but with rapid fluctuations which appear to be unrelated to any change in the lithology, and which Forkner et al. suggest might be related to short-term anoxia events not recorded in the rock record.

 

Compound tracks through the Cenomanian–Turonian boundary interval relating to productivity before, during, and after the event. For the main the Cenomanian–Turonian boundary interval section, the concentration of biomarkers derived from algae such as C₂₇, C₂₈, and C₃₀steranes (24-n-propylcholestanes), and 4α-methyl-24-ethylcholestane 20R decreases significantly relative to concentrations of those derived from bacteria, which increase moderately with variations. This suggests that the record of productivity variability we interpret is reliable and is not simply a record of poor preservation of the organic fraction. Of note is the interval in all track from about 473 feet (144 m) to about 479 feet (146 m) where organic geochemical measurements return the most erratic results. By applying the most recently published timescales through this interval, it is possible to calculate that the productivity cycles of biomarker decline and recovery can vary from about 26 thousand years at the shortest to about 130 thousand years at the longest. These productivity cycles occur within individual lithofacies internal to single lithocycles. Fornkner et al. (2021).

Isoprenoids can be derived from chlorophyll side chains produced by photosynthetic Algae, although other organisms do produce them, including Cyanobacteria and some Archaeans. Notably, head-to-head isoprenoids such as biphytane are produced by marine Archaea. Unfortunately, isoprenoids are found at very low concentrations throughout the core, although some fluctuations can be observed during the Cenomanian–Turonian boundary layers, and biphytane and its diagenetic products are only ever found at trace levels, and often drop below detectability levels. Studies of the Cenomanian–Turonian layer in other sections have suggested that there might have been blooms of opportunistic Archaea during this interval, but this cannot be detected in the Portland-1 core.

A number of biomarkers remain relatively constant on either side of the Cenomanian–Turonian boundary layers, but fluctuate greatly during the boundary interval. Previous work on the Portland-1 core and other cores from the same area have been studied extensively to determine sedimentation rates. These studies have led to a calculated sediment accumulation rate of 0.93 cm per thousand years in the upper part of the Cenomanian–Turonian boundary, using calculations that include radiometric dates from bentonite layers, and orbital time scales. Calibrating this with the observed fluctuations in biomarker ratios suggests that productivity fluctuations were occuring on cyclical scales of between 26 and 90 thousand years, with individual biological collapses happening in as little as 3200 years.

One possible cause of influxes into the shallow, enclosed, Western Interior Seaway during the Cenomanian–Turonian boundary period that has been previously suggested is sea level rises, Evidence for such changes has been found in the Tethys Ocean, where repeated cycles of carbonate platforms being replaced by deeper sediments have been observed. Such an increase in water volume would provide relief from the effects of stagnation, but cannot explain the drastic changes in water column ecology observed by Forkner et al., which appear to happen on a much finer scale. Forkner et al. were unable to find any references to previous examples of such rapid changes in organic composition of a rock sequence, particularly one one independent of changes in the lithology, and conclude that the drivers these changes were clearly independent of the drivers of lithology changes.

Studies of the lithology and astronomical forcing cycles recorded in the Portland-1 core have previously concluded that the carbonate-mudstone cycle here (which would have been driven by changes in sealevel) would have lasted about 100 000 years. The biological productivity cycle, however, is clearly working on a much shorter, more erratic, and independent timescale. Forkner et al. cannot rule out the possibility that some shorter Milankovitch-band processes was occurring in the Western Interior Seaway, but the irregular nature of the cycles makes this unlikely, as does the fact that they are not seen outside the Cenomanian–Turonian boundary interval.

Forkner et al. suggest that these biomarker cycles may have been driven by changes in primary productivity (i.e. photosynthesis), and the subsequent decay of organic matter. During the intervals on either side of the boundary, more reducing conditions prevailed, probably due to higher rates of organic decay. During times of extreme stress within the boundary period, the amount of primary production dropped, and there was a drop in the amount of organic matter in the water column, and therefore the amount of decay that could occur. However, the driver of this stress, and the cause of the erratic cycle it was following, remain unclear.

A cause of environmental stress unrelated to sealevel changes or orbital forcing and operating on rapid and erratic timescales could plausibly be volcanism. Volcanism has the potentially to disrupr Algal productivity rapidly, and would not cause any change in the depositional environment (which changes in sealevel related to Milankovitch forcing would do). A number of other cores from the Western Interior Seaway (including Eagle Ford, Boquillas, and Bouldin Flags) contain numerous bentonite layers (caused by volcanic ash falling on water then settling to the bottom), which have been used to determine the age of the sediments and the rate at which they were accumulating. Volcanism can impact Algal productivity in a number of ways, from lowering light levels to altering the pH of the water. While this cannot be proven from Forkner et al.'s current work, it would potentially have left detectable signs which could be revealed by future investigations. Either way, these findings appear to support the idea that the Cenomanian–Turonian Extinction Event was caused by a prolonged breakdown in environmental conditions rather than a single catastrophic event.

The Cenomanian–Turonian boundary reflects a profound change in environmental conditions on a global level, although the record of this varies from location to location. Geochemical examination of organic molecular fossils preserved in the Portland-1 core, a nearly-continuous core of sediment recovered from the Western Interior Seaway of North America, shows a record of extreme environmental variability not previously observed, with a generally higher level of oxygenation than before the crisis, prior to previous assumptions about a single, massive, anoxia event driving the crisis. Instead, the environment seems to have undergone a series of smaller, but still significant, crises, operating on an irregular cycle divorced from Milancovich forcing and sealevel changes. Forkner et al. hypothesise that this could have been driven by volcanic episodes, which tend to be erratic in their timing. A single, massive, volcanic event has previously been suggested as a possible cause of the Cenomanian–Turonian Extinction Event, injecting vast amounts of material into the atmosphere and oceans, and leading to significant changes in seawater pH, global temperature, and the hydrological cycle, but Forkner et al.'s evidence points towards a more prolonged period of change, with periods of high organic productivity punctuated by sudden collapse. This repeated stressing of the marine environment would have challenged the biota of these ecosystems, potentially causing the observed extinctions.

See also...

Online courses in Palaeontology.  

Follow Sciency Thoughts on Facebook.

Follow Sciency Thoughts on Twitter. 

Sakhalinencyrtus leleji: A new species of Encyrtid Wasp from Middle Eocene Sakhalinian Amber.

The Encyrtidae are a large family of parasitoid Chalcid Wasps, primarily targeting members of the Hemiptera (True Bugs), although some target of Ticks and others are hyperparasites, with their larvae growing inside the parasitic larvae of other Wasps. The first known fossil species assigned to the family, Encyrtus clavicornis, was described from an Oligocene shale from Rott in Germany in 1938. Since this time a further eighteen species have been discovered, Archencyrtus rasnitsyni, Sugonjaevia sakhalinica, Kotenkia platycera, and Encyrtoides pronotatus, from Middle Eocene Sakhalinian Amber, Eocencyrtus zerovae, Eocencnemus sugonjaevi, Eocencnemus vichrenkoi, Eocencnemus gedanicus, Glaesus gibsoni, Rovnosoma gracile, Sulia glaesaria, Protocopidosoma kononovae, Dencyrtus vilhelmseni, Archaeocercus schuvachinae, Trjapitzion cylindrocerus, Ektopicercus punctatus, and Efesus trufanovi, from Late Eocene Baltic Amber, and Copidosoma archeodominica, from Miocene Dominican Amber.

In a paper published in the Journal of Hymenoptera Research on 24 August 2021, Serguei Simutnik and Evgeny Perkovsky of the I.I. Schmalhausen Institute of Zoology of the National Academy of Sciences of Ukraine, and Dmitry Vasilenko of the Borissiak Paleontological Institute of the Russian Academy of Sciences, and the Cherepovets State University, describe a new species of Encyrtid Wasp from Middle Eocene Sakhalinian Amber.

Sakhalinian Amber is mainly collected on a beach near the village of Starodubskoye, close to the mouth of the Naiba River in Dolinsk District on Sakhalinian Island in the Sea of Okhotsk in the Russian Far East. For a long time the age of this amber was uncertain, but in 1999 it was found in situ in strata of the Naibuchi Formation, making it Middle Eocene in origin, and older than the Baltic and Rovno ambers.

The new species is named Sakhalinencyrtus leleji, where 'Sakhalinencyrtus' implies an Encyrtid Wasp from Sakhalinian Amber, and 'leleji' honours Arkady Stepanovich Lelej for his expertise on the Hymenoptera. The species is described from a single male specimen preserved within a piece of Sakhalinian Amber, which also contains an undescribed female Ant.

 

(A) Piece of Sakhalinian Amber containing inclusions (B), (C) syninclusion of Mymaridae, female (B) dorso-lateral (C) ventral (D)–(F) Sakhalinencyrtus leleji holotype male: (D) antennae, head, mesosoma, ventral (E) antennae, head, frontal (F) antennae, head, and anterior part of metasoma, dorso-lateral. Simutnik et al. (2021).

The specimen is 0.9 mm in length, and brownish black in colour. The lower jaw is longer than the upper, the head is wider than the thorax. The eyes are small and almost circular, although details of the face are unclear as this has been deformed during preservation. The sockets in which the antennae are fitted are half way between the lower margin of the eyes and the margin of the mouth. The first segment of the antannae is extended and flattened, being four times as long as it is wide. The mesosoma (middle section of the body) is shorter than the metasoma (final section), and is not flattened. The forewing is glassy in appearance, with a row of hairs on its basal margin. 

 

Sakhalinencyrtus leleji, holotype male (A) head and mesosoma, dorsal (B) venation of fore and hind wings, dorsal (C) venation of fore and hind wings, metasoma and part of genitalia, ventral, cs, covering setae. Simutnik et al. (2021).

See also...

Online courses in Palaeontology.  

Follow Sciency Thoughts on Facebook.

Follow Sciency Thoughts on Twitter. 

Cattle herder killed by Crocodile in Gujarat State, India.

A cattle herder has died after being attacked by a Crocodile in the Bharuch District of Gujarat State, India, on Sunday 22 August 2021. Ramji Mansingh Rabari, 52, from the village of Limodara, was standing in the River Narmada, when he was attacked. A witness to the event who witnessed the event quickly summoned help from the nearby village of village of Ladwavad, but when villagers arrived with boats he had already bled to death.

 

Crocodiles by a river in Gujarat State, India. Indian Express.

There are three species of Crocodilians found in India, the Saltwater Crocodile, Crocodylus porosus, the Mugger Crocodile, Crocodylus palustris, and the Gharail, Gavialis gangeticus. Of these the Gharail is unlikely to be found in a waterway of this type, and is generally a Fish-eater, not prone to attacking Humans.  Muggers are smaller that Saltwater and Nile Crocodiles, with males reaching about 3.5 m and females about 2.5 m, and are generally less considered less dangerous, as their preferred prey is animals smaller than Humans. However, as with other Crocodilians, the females can be highly aggressive during the summer, when they are nesting, leading to occasional Human fatalities.

Mugger Crocodiles were formerly found across South Asia from Iran to Myanmar and Nepal to Sri Lanka, but they are thought to be extinct in Myanmar, Bhutan, and Bangladesh, and the species is considered to be Vulnerable under the terms of the International Union for the Conservation of Nature’s Red List of  Threatened Species.

Crocodiles were previously uncommon in Bharuch District, but their numbers have risen sharply in recent years, possibly due to altered water flows caused by the construction of the Sardar Sarovar Dam. This rise in Crocodile numbers has brought the Animals into contact with Human populations that are not used to their presence, leading to a rising number of fatalities. 

See also...

Follow Sciency Thoughts on Facebook.

Follow Sciency Thoughts on Twitter. 

Interpreting the gender identity of the Suontaka Vesitorninmäki burial.

Reports of women buried with weapons always generate considerable interest in archaeology. One notable example of this is the Suontaka Vesitorninmäki grave from southern Finland, which has been interpreted as a woman buried with two swords, based upon the feminine clothing of the individual, and the presence of jewellery, which is not generally found in male burials of the period (the grave has been dated to between 1050 and 1300 AD). This site has been held up as an example of a powerful woman in a late Iron Age/early medieval society since its discovery in the 1960s, and was on permanent display as evidence of a female leader at the National Museum of Finland from 1995 to 2016, with one of the swords from the site being on display in the ‘Meet the Vikings’ exhibition at the National Museum of Denmark as a woman's weapon.

In a paper published in the European Journal of Archaeology on 15 July 2021, Ulla Moilanen of the Department of Archaeology at the University of Turku, Tuija Kirkinen of the Department of Cultures at the University of Helsinki, Nelli-Johanna Saari and Adam Rohrlach of the Max Planck Institute for the Science of Human History, Johannes Krause of the Max Planck Institute for Evolutionary Anthropology, Päivi Onkamo of the Department of Biology at the University of Turku, and Elima Salmela of the Organismal and Evolutionary Biology Research Programme at the University of Helsinki, present a review of our understanding of the Suontaka grave, re-examining the original field documentation of the site and presenting new microscopic analysis of material from the grave and a DNA analysis of the genetic identity of the individual from the grave.

 

Location of the Häme (Tavastia) region in Finland, with Suontaka marked with a red dot. Moilanen et al. (2021).

For much of the history of archaeology, bodies have been identified as male or female, depending on analysis of skeletons and/or the presence of grave goods interpreted as masculine or feminine, with genetic analysis recently added to the available repertoire of techniques. However, simply dividing Human populations into men and women is sometimes an oversimplification, with a range of genetic, chromosomal, and hormonal conditions known to blur the biological lines between the sexes, and people sometimes self-identifying in ways that differ from their biology. Recent developments in neurology have demonstrated that our brains do not neatly divide into 'male' and 'female' groups, but show a variation in personality, cognition, and behaviour that is individualistic rather than coupled to biological sex.

Since the 1970s, anthropologists have come to an understanding that biological sex and socially determined gender are different things, with gender roles essentially learned, with people tending to conforn to the norms expected of their body-type, while biological sex is an expression of chromosomal, hormonal, anatomical, and physical features.

Modern western perceptions of a binary division of the sexes tend to dominate in archaeology, but other cultures have had different perspectives. Early medieval cultures had their own views on masculinity and femininity, but it is unclear how fixed these roles were in their perception, and to what extent they could be modified by circumstances. Traditionally, medieval societies have been perceived as having very distinct male and female roles, but more recent studies have suggested that they may have been more flexible in their views.

The practice of identifying the gender of individuals by the grave goods buried with them adds further confusion to this issue, since we cannot be confident about how rigid these rules were. The presence of swords in medieval graves in northern Europe is generally taken as a strong indicator of masculinity, and as having the status as a member of a warrior class, but this secondary role, one as a class identifier rather than a gender one could potentially confuse the issue. Individuals identified as female by their body type, and who are buried with jewellery (usually taken as a sign of femininity), have occasionally been found with axes, spear- and arrow-heads, but swords are much rarer, and generally taken as cause for comment. Notably, bodies which are identified as female, and which are buried with swords, are generally lacking in 'feminine' grave goods such as jewellery, possibly suggesting that women were allowed to take on masculine gender under some circumstances in Scandinavian culture, but that once they had done so, were expected to conform to their new gender identity. Working from this assumption, the presence of weapons in 'female' graves becomes problematic, and has led to archaeologists sometimes looking for more explanation than might be merited, such as assuming that graves containing both weapons and jewellery must have originally been double burials, despite there being no evidence for a second body. Such investigations potentially tell us more about the cultural assumptions of the archaeologists excavating the burial than those of the people who dug the grave in the first place.

Discovered in 1968, the Suontaka Vesitorninmäki gained fame for the mixture of 'masculine' and 'feminine' grave goods found within a single burial. The most notable item was a bronze-hilted sword with Urnes style ornamentation (slim, stylised animals woven into patterns, typically indicative of late eleventh or early twelfth century manufacture), with the grave also containing a second, hiltless sword blade, two oval brooches, a small penannular (ring shaped, with part of the circumference missing) brooch, a twin-spiral chain-bearer, and a sickle. Traditionally, swords are considered to be masculine items in burials, while jewellery is feminine. Sickles can be found in graves associated with either gender in Finland, but are more common in female burials. All of the objects point towards a burial in the late eleventh or early twelfth century AD, which would coincide with the Crusade Period in Finland (during which Sweden invaded southwestern Finland, officially to convert the pagan Finns to Christianity, although it is likely that the Finns were already Christian by this point). A subsequent radiocarbon date obtained from a fragment of femur obtained from the grave indicated the burial took place between 1040 and 1174 AD.

 

The objects found in the Suontaka grave. (A) bronze-hilted sword (NM 17777:1); (B) hiltless sword (NM 17777:2) with silver inlays (inset); (C) two oval brooches with textile fragments (NM 17777:4–5); (D) twin-spiral chain-bearer (NM 17777:6); (E) sheathed knife (NM 17777:3); (F) penannular brooch (NM 17777:7); (G) sickle (NM 17777:8). Moilanen et al. (2021).

The original excavation of the Suontaka Vesitorninmäki site was carried out in October 1968, after the bronze-hilted sword was discovered during work on a water pipeline. The discovery of the sword led to archaeologist Oiva Keskitalo investigating to the site. Keskitalo subsequently discovered an area of darker soil cross-cutting the pipeline trench, further investigation of which revealed the grave. The pipeline intersected the upper right corner of the grave, which was where the sword was located. The distance between the sword and the skeletal remains and other artefacts within the grave was not recorded, but some of the dark soil needed to be removed to expose these, whereas the sword appears to have been on top of the dark layer, making it likely that the sword was not part of the original burrial assemblage. No other graves have been found in the area, so the grave was either a solitary burrial, or is the sole survivor of a burial ground which has otherwise been lost.

The context of the find makes the interpretation of the sword difficult; the site had been disturbed by pipeline workers before archaeologists were called in, and the site was excavated in late autumn, with temperatures dropping as low as -10°C. However, it would have been warmer at the bottom of the pit, so the field observations should be seen as reasonably reliable. The position and shape of the skeleton were documented, with the tibias, femora, pelvis, elbow joints, ribs, and skull all in place when they were uncovered, although they were in an advanced state of decomposition and almost entirely composed of soft material which could not be recovered, with the exception of two femora fragments. 

 

(A) Plan of the Suontaka burial. ‘Täckdike’ marks the water pipe trench which led to the discovery of the grave. (B) Artist’s reconstruction of the burial, showing the position of the objects on the body. Drawing by Veronika Paschenko. Moilanen et al. (2021).

The rarity of swords in graves which also contain 'feminine' grave goods led to some controversy in how the Suontaka Vesitorninmäki burial should be interpreted. The most obvious possibility, based upon 1960s archaeologists' understanding of early medieval graves, was that this was a double burial, and that there must originally have been two bodies in the grave. Confronted with a grave containing a skeleton associated with two brooches and a sword, Keskitalo searched for evidence of a second body, but could find none. The grave was found to have an even floor, upon which the body had been placed, with no evidence of a coffin, and was apparently two small for a second corpse. It is possible that a second body could have been placed on top of the first body, something which is known to accelerate the decay rate of the upper body (or bodies), but the grave lacks any sign that would be associated with that, such as varying soil colouration caused by an upper decomposition layer, and the only artefact that does not appear to have been placed in context with the skeleton is the bronze-hilted sword.

The sword without a hilt was located on the left side of the pelvis, with the sheathed knife on top of it. The two oval brooches, and associated fibres, were located beneath the shoulders, which implies the body was dressed in the typical female clothing of the day. The chain bearer lacked associated chains and was located in the centre of the chest, which may imply it was worn as a pendant rather than as an actual chain-bearer, something typically associated with female burials. The penannular brooch was located at about waist level, the sickle placed upon the chest. Items placed on top of bodies tend to move downwards, although this is likely to be less notable in an instance like the Suontaka Vesitorninmäki grave, where no coffin was used, enabling sediment to replace tissue as it decayed. This supports the idea that all the objects other than the bronze-hilted sword were placed directly on the body, rather than on another corpse that subsequently decomposed completely.

No samples of soil were deliberately collected at the time of the excavation, but small amount of soil was excavated along with the recovered femur fragments, which Moilanen et al. analysed for fragments of hair or textiles. They were able to recover a total of 23 Mammal hair-fragments, mostly between 0.2 and 2 mm in length, and three fragments of Bird feathers, between 0.2 and 0.5 μm. Seven of the hairs were unidentifiable. Fourteen of the hairs came from Sheep (i.e. wool), of which nine were naturally coloured (six white and three brown) and five had apparently been died (three bluish green and two blue). In addition there was one hair identified as either coming from a Fox or a Mustelid, and one identified as either Rabbit or Hare, the latter of which was purple in colour, again probably due to dying. None of the feather fragments could be identified. 

 

Examples of identified animal hairs from the soil sample. (A) Leporidae; (B) Vulpes vulpes or Mustelidae (K20); (C) Ovis aries (K13); D: Aves (K19). Moilanen et al. (2021).

The limited amount of bone material recovered from the grave prevented any osteological analysis, but it did prove possible to extract DNA from the sample. This sample was again limited in nature, preventing a full genetic analysis, but did allow for sex identification, as this is one of the tests which requires the least amount of data.

Surprisingly, the most likely outcome of this test was neither an XX ('normal female') or XY ('normal male') karyotype, but rather an XXY karyotype, i.e. a male (the presence of an Y chromosome usually determines maleness), but with a second X chromosome, a condition called Klinefelter syndrome. In modern populations about 1 in 576 male Humans have Klinefelter syndrome, the majority of whom will never show any symptoms of the condition, but in some cases symptoms are present, including infertility, small genitalia, breast development, and occasionally a small vaginal opening beneath the penis. There are also some psychological symptoms that are sometimes associated with the condition when physical symptoms are not present, but since these are closely linked to cultural background, and observed in men who have been told they have it, it is difficult to assess how they could be related to twelfth century Finland.

The Suontaka Vesitorninmäki grave appears to have contained a single individual, dressed in a way that would have been considered feminine at the time. The grave contains a hiltless sword associated with the body, the other, bronze-hilted, sword appears to post-date the original burial. It is possible it was deliberately placed at the grave site by a later generation; such hiding of swords in burial mounds and other special locations for magical purposes is known to have been practiced. However, the hiltless sword was clearly buried with the body, and presumably therefore relates to the person in the grave. The sword bears no sign of battle-damage, and the hilt may have been deliberately removed (although it might have been made of material which has degraded post-burial), which might be a way of indicating the owner of the sword was less than completely masculine. The presence of an apparently intentionally unusable sword is curious, as the burial occurred in a time of violent cultural disturbance, with a number of hillforts being erected in the area at the time, and other swords locally recovered from the period often showing battle damage.

The hairs recovered from the grave imply the presence of both naturally coloured and dyed fabrics, and possibly garments made from fur or Animal skin; such materials were often used to make cloths linings, mittens, pouches, and knife sheaths in early medieval Finland. The presence of a Rabbit or Hare hair might imply a garment made from a textile made from Rabbit fur, or blended Rabbit fur and wool, both of which would have been high value items at the time. The feather fragments might relate to a pillow or other bedding item. All of this points towards an individual with some social standing in the society in which they lived.

The possibility that the individual in the grave was a male with Klinefelter syndrome is not unprecedented in archaeology; other individuals with the condition have been reported from Viking Age Iceland, early Neolithic Germany, and possibly the Orkney Islands in the Viking Age, although none of these graves appeared to be otherwise atypical for the cultures that produced them. Based upon this, the discovery of an individual with Klinefelter syndrome in a grave bearing a mixture of goods with different gender-associations is a novel one.

However, it should be remembered that Klinefelter syndrome does not necessarily have any visible symptoms, and that people's personal gender identity sometimes varies considerably from their anatomical appearance, and that it is dangerous to make assumptions about the Suontaka Vesitorninmäki individual's gender identity purely based upon their karyotype.

The possibility that the individual did show some noticeable symptoms of Klinefelter syndrome cannot be completely overlooked, however. The age of the individual is unknown, but it is likely they had lived past puberty, when any such symptoms would have become more obvious. Gender roles tend to be shaped by both an individual's perception of themselves, and the way in which their wider society views them. In Early Modern Finland masculinity is known to have been closely related to the ability to sire children, and a man who could not do so was likely to be seen as less that fully masculine, although it is unclear how far back in time these cultural assumptions can safely be projected.

Clothing is also an important manifestation of personal identity. This appears to have been well understood in medieval Europe, where there are numerous tales of female warriors adopting male dress and identities. In early modern Finland cross-dressing was strongly associated with anatomical ambiguity, and anyone wearing gender-inappropriate clothing was likely to be refferred to as a hermaphrodite (although, again it is hard to judge how far back in time this assumption can be extrapolated). Seen in this light, an individual buried with a mixture of male and female accoutrements could quite possibly have been anatomically non-binary. However, our current understanding of the culture of early medieval culture would predict such an individual would be viewed in a fairly negative light, whereas the context of the Suontaka Vesitorninmäki burial implies an individual held in high regard by those that buried them. 

Early medieval Scandinavia is generally viewed as having had an ultra-masculine culture, with strongly defined gender roles, in which it would be seen as shameful for a man to adopt women's clothing. However, there is some evidence that individuals with more ambivalent gender identities could have been involved in ritual practices, and would therefore have been tolerated, and even valued. A twelfth century grave from Vivallen in western Sweden was found to contain a male body buried in female clothing, but with masculine grave goods. This grave has been interpreted as that of a shaman, possibly deriving from the Sámi culture of northern Scandinavia. 

A binary view of gender assumes that there is a single way of being a man and a single way of being a woman. The Vivallen and Suontaka Vesitorninmäki burials suggest that medieval Scandinavian societies may not always have seen the world in this way. The Suontaka Vesitorninmäki burial in particular appears to present evidence of a non-binary individual being able to hold a valued role in such a society, despite being willing to be conspicuously different from the norm. It is of course possible that such an individual was respected because of their birth rank rather than because of their difference; an unusual person from a powerful and well-connected family would probably be tolerated more easily that one from a less prominent family, since people would seek to avoid conflict with that person's relatives, no matter what they might privately think. The presence of a sword in the grave may be indicative of this, since swords were a valuable artefact at the time, and not necessarily available to every male member of the population. The individual does appear to have been a local; the brooches are of a local type and nothing in the grave appears to indicate a foreign origin, whereas other Scandinavian graves (such as Vivallen) in which males were buried with female items have been interpreted as being of strangers, buried with inappropriate items as a sign of disrespect.

In early medieval times, Suontaka does not appear to have been a remote location; the area is surrounded by other archaeological sites, including a hillfort, sacrificial stones, cemeteries, and settlement sites surrounded by ancient fields. The village was probably one of the more important in the region, possibly the site of local assemblies. The presence of a burial with grave goods including feather bedding, fur cloths and a silver-inlaid sword would appear to support this view, as well as the likelihood that the individual buried came from a wealthy and well-connected family, and might therefore have been tolerated a degree of cultural freedon not accorded to all members of society. However, it is also possible that the people of early medieval Finland were more flexible in their views of gender roles than has generally been assumed. The Suontaka Vesitorninmäki individual appears to have been buried with items associated with both genders, and those items appear to have been indicative of a degree of wealth. This makes it less likely that that person had been forced into a gender ambivalent role as a mark of humiliation, and more likely that they were able to express their identity freely, in contrast to the normal expectations of their society (or our expectations of it) and still hold a relatively high position in that society. The addition of a second, high-status sword at some time after the initial burial would seem to imply that the individual retained their high status after death, and was seen as important by subsequent generations.

The Suontaka Vesitorninmäki  individual was previously interpreted as a woman buried with two swords. The grave was clearly well stocked with high value items, but it is likely that only one of the swords was part of the original grave assemblage, with the second being added later. The individual in the grave now seems less likely to have been female, and more likely to have been a male individual with Klinefelter syndrome. The individual appears to have been a male, but one who would not fit the expected norms of a masculine society in which warfare was celebrated. Nevertheless, the individual appears to have been a respected member of that society, implying that that society was more open-minded about individuals who did not fit typical gender roles that has previously been assumed, although to what extent this was dependent on that person's pre-existing social rank is unclear.

See also...

Follow Sciency Thoughts on Facebook.

Follow Sciency Thoughts on Twitter. 

Seventeen confirmed deaths and forty two still missing as flash floods hit Tennessee.

Seventeen people, including several young children, have now been confirmed dead, and another forty two are missing following a series of floods in Humphreys County, Tennessee. Slightly over 43 cm of rain fell in the area around the town of Waverly within 24 hours over the weekend of 21-22 August 2021, exceeding previous rainfall records by more than 8 cm, and causing a series of flood events that swept away many homes and businesses in the area.

 

Flooding around the town of Waverly in Humphreys County, Tennessee. Nashville Fire Department.

The rainfall was caused by a combination of a high pressure system over Texas and a low pressure system over the Mid Atlantic, which pushed waves of humidity laden air to be pushed northwards from the Gulf of Mexico. Low pressure systems are caused by solar energy heating the air above the oceans, which causes the air to rise leading to an inrush of air. Meteorologists have warned that such storms are likely to become much more common with rising global temperatures. Storms of this magnitude were formerly expected roughly once every hundred years in the Tennessee, but this is the second such event this year, following a storm to the south of Nashville in March.

See also...

Follow Sciency Thoughts on Facebook.

Follow Sciency Thoughts on Twitter. 

 

Sengis (Elephant Shrews) from the Late Oligocene Nsungwe Formation of southwestern Tanzania.

The Macroscelideans (also termed Sengis, or Elephant Shrews) are an enigmatic group of small insectivorous Mammals, known only from continental Africa. They are noted for their rapid movement, driven by powerful hind limbs, and elongate, flexible snouts, with 20 species known today, grouped into six genera. The history and relationships of this group were difficult to unravel. They have been linked to the Mixodectids (an extinct group of insectivorous Mammals related to the living Colougus of Southeast Asia), the Glires (Rodents and Lagomorphs), the Menotyphla (now rejected theoretical group of Mammals which included Treeshrews, Colougus, Primates, and some extinct groups), and the Condylarths (another rejected group, which comprised species now considered to be early Perissodactyls and Artiodactyls). To make matters more confusing, some fossils now attributed to the Macroscelidea were previously considered to be Hyraxes or Marsupials. More recently genetic studies of Mammal classification has led to Macroscelideans being placed within the Afrotherians, a group which also includes Aardvarks, Tenrecs, Hyraxes, Sirenians, and Elephants. Subsequent re-evaluations of the morphology of African Mammals has led to evidence supporting the Afrotherian hypothesis, which is now generally accepted by zoologists.

A lack of samples from the Palaeogene-Neogene Transition zone obscures our understanding of the evolutionary history of Sengis as a group. The Palaeogene fossil record of the group comprises two subfamilies from North Africa, both of which are considered to be extinct. The Subfamily Metoldobotinae comprises a single genus, Metoldobotes, known only from the Early Oligocene Fayum Depression of Egypt, while the Subfamily Herodotiinae includes four genera, from the Eocene of Algeris, Libya and Tunisia, and the Oligocene of Egypt. Some possible Sengi material is known from Namibia, but this has not been confidently assigned to the group, and there is some dispute as to the age of the deposits from which these specimens were obtained, which may have been of Eocene, Oligocene, or Miocene origin.

The earliest known Neogene Sengi fossils date from the Miocene of Kenya, South Africa, and Namibia, and are assigned to the Myohyracinae, another extinct subfamily with dentition interpretted as indicative of a herbivorous diet. This leaves a nine million year gap in the fossil record of the group, with members of modern groups first appearing about 18 million years ago. 

The deposits of the Rukwa Rift Basin of southwestern Tanzania provide a rare insight into the Vertebrate faunas of the Middle Cainozoic of Africa. The Nsungwe Formation is a series of roughly 25 million-year-old fossiliferous fluvial deposits forming part of the Red Sandstone Group. This formation has produced numerous fossil Invertebrates, Fish, Anurans, Lepidosaurs, and a wide range of Mammals, including Sengis.

In a paper published in the journal Historical Biology on 23 July 2021, Nancy Stevens and Patrick O’Connor of the Department of Biomedical Sciences and Center for Ecological and Evolutionary Studies at Ohio University, Cassy Mtelela of the Department of Geosciences at the University of Dar Es Salaam, and Eric Roberts of Earth and Environmental Sciences at James Cook University, describe Oligocene Sengi specimens from the the Late Oligocene Nsungwe Formation of southwestern Tanzania, which they ascribe to the subfamilies Myohyracinae (previously known only from the Early Oligocene of Egypt) and Rhynchocyoninae (the subfamily in which all extant Sengis are placed.

The Oligocene sedimentary deposits of the Rukwa Rift Basin are thought to represent the earliest known Cainozoic sedimentary record of rifting in the Western Branch of the East African Rift System. Fossil exposures are found along the Songwe River Valley, forming part of a laterally continuous series of interbedded fluvial sandstones, floodplain and channel fill palaeosols, lacustrine siltstones, and devitrified airfall tuffs, known as the Songwe Member of the Nsungwe Formation. Fossils tend to be discovered as isolated small specimens, including numerous teeth, jaws, and postcranial elements, from layers within this member interpreted as flash flood deposits. These beds are bracketed between volcanic ash layers from which radiogenic dates have been obtained, and are confidently dated to about 25 million years, making them Late Miocene in age.

 

Geological context. Specimens were recovered from the Songwe Member of the late Oligocene Nsungwe Formation in the Rukwa Rift Basin of southwestern Tanzania. (A) Geographic position of the Rukwa Rift Basin in eastern Africa (Tanzania shaded) and (B) Digital elevation model showing the outcrop distribution of the Nsungwe Formation study area at the southern end of the Rukwa Rift Basin in the Songwe Valley. Stevens et al. (2021).

The first specimen described is placed within the Myohyracinae and given the name Rukwasengi butleri, where 'Rukwasengi' indicates a Sengi from the Rukwa Rift Basin, and 'butleri' honours Sengi expert Percy Butler, who first described the Family Macroscelidea. The specimen comprises partial right maxilla preserving teeth M2-M3 (the second and third molars).

 

Nsungwe formation Myohyracine. Photograph (A) and digital renderings (B)–(E) of the late Oligocene Rukwasengi butleri (RRBP 05409, holotype) upper right molars (M2-3) in occlusal (A), (B), lingual (C), buccal (D), and posterior (E) views. Photograph of Myohyrax oswaldi (KNM-RU 3763) in occlusal view (F) for reference. The lead line to “fs” calls out the small fossette on M3. Scale bars equal 1 mm. Stevens et al. (2021).

The teeth of the specimen are both slightly worn. The M2 molar is 2.45 mm in length and 3.3 mm in width, with the broadest point near the base of the mesial cusps. The paracone is slightly taller than the metacone, and placed more bucally. The tooth also has a strong, mesially curved lingual sulcus. The protocone and hypocone are directed anteriorly and have sharp lingual margins. There are three rounded fossettes on the occusal surface, two on the buccal half 1of the tooth, and a smaller one positioned centrally. The M2 molar is triangular and has three roots. It measures 1.2 mm by 1.5 mm.

The second specimen is assigned to the Rhynchocyoninae, and named Oligorhynchocyon songwensis, where 'Oligorhynchocyon' refers to the fact that it is a member of the Rhynchocyoninae from the Oligocene, and 'songwensis' means 'from Songwe', in reference to the Songwe River. The specimen comprises a left P4 (fourth premolar) tooth.

 

Nsungwe formation Rhynchocyonine. Photograph (A) and digital rendering (B)–(D) of the late Oligocene Oligorhynchocyon songwensis (RRBP 08086, holotype) left lower fourth premolar in occlusal (A), (B), buccal (C), and lingual (D) views. Photograph (E) and digital rendering (F-H) of Oligorhynchocyon songwensis (RRBP 07433, referred specimen) upper left molar (M2 or M3) in occlusal (E), (F), buccal (G), and lingual (H) views. Scale bars equal 1 mm. Stevens et al. (2021).

The tooth is a molariform premolar with two roots, and is quite worn. It is 4.1 mm in length and 1.95 mm in width, with the widest point across the protoconid and metaconid. The tooth strong anterobuccal cingulid, although it has a faint rugosity in that position. The paraconid is low and wide, and only half the height of the other trigonid cusps. This paraconid is distinct, but linked to the protoconid by a small paracristid, which ascends along the posterobuccal aspect of the cusp. Another preprotocristid descends along the anterolingual aspect of the protoconid, with the two meeting in a notch just posterobuccal to the paraconid. The protoconid and metaconid are aligned transversely, subequal in size, and connected by a narrow protocristid, with the two forming an unbroken posterior trigonid wall. The hypoconid and entoconid are also aligned transversely and subequal in size. The trigonid and talonid basins are steeply sloped lingually and cusp heights are uneven across the tooth; the protoconid and metaconid approximately 50% taller than the paraconid, entoconid and hypoconid.

A third specimen, RRBP 07433, is a slightly worn three-rooted left upper molar (M2 or M3). This is also tentatively referred to Oligorhynchocyon songwensis, as they appear compatible in size, and the specimen appears to belong to a member of the Rhynchocyoninae. This specimen is 2.8 mm in length and 2.6 mm in width, with cusps largely subsumed in crests. A large paracone is connected to a well-developed anteriorly projecting parastyle by a preparacrista. The anterior cingulum is pronounced. A wide preprotocrista extends halfway to a point between the paracone and the parastyle. Only the bases of the roots remain, with these being subequal in size.

These specimens represent the oldest example of a Myohyracine from East Africa, and the oldest known, and first Palaeogene, example of a Rhynchocyonine. The oldest know Sengis are Eocene in age, but to date very few pre-Miocene specimens have been discovered, with all of these early specimens referred to extinct families, rather than the living Rhynchocyonine.

The previously oldest members of the Rhynchocyonine. were Miorhyncocyon meswae, from the early Miocene Meswa Bridge locality in Kenya, Miorhynchocyon clarki and Miorhynchocyon rusingae, both from the early Miocene Songhor locality, also in Kenya, and Brachyrhynchocyon and Hypsorhynchocyon, from the early Miocene Northern Sperrgebiet locality in Namibia. Some possible Rhynchocyonines have also been recorded from the Eocene Eocliff locality in Namibia, and the early Miocene of Uganda, but these are not well dated nor confirmed taxonomically.

Members of the Myohyracine have previously been recorded from the Miocene Chamtwara and Songhor localities in Kenya, and the Miocene of Namibia, with the youngest known specimens being from the Fort Ternan locality in Kenya and the Bosluts Pan in South Africa, both being about 13 million years old. 

The presence of members of the Rhynchocyonine and Myohyracine in the Nsungwe Formation shows both were present in East Africa by about 25 million years ago, before the Palaeogene-Neogene Transition, providing an important insight into the history of the group, and underscoring the importance of these deposits for our understanding of the development of modern African Mammal faunas.

See also...

Online courses in Palaeontology. 

Follow Sciency Thoughts on Facebook.

Follow Sciency Thoughts on Twitter.