An embryonic Synapsid from the Early Triassic of South Africa.

 The persistence of egg-laying in modern Monotremes has led evolutionary biologists to conclude that this is likely to have been the ancestral state in the Synapsids, the group from which the Mammals arose. However, fossil evidence for this has been surprisingly absent. The earliest known potential fossil amniotic egg comes from the Permian of South America, and has been attributed to a Mesosaurid Sauropsid (a group not closely related to Synapsids of Mammals). This specimen preserves an immature skeleton curled in a position consistent with having been in an egg at the time of death, but no actual eggshell (not altogether surprising, as the earliest amniote eggs are not predicted to have been mineralised). The earliest amniotic egg fossils with both embryonic remains and eggshell come from Sauropodomorph dinosaurs from the Early Jurassic of Gondwana. Some potential eggs associated with Synapsid Pelycosaurs from the Early Permian of North America are not considered to be reliable, as neither embryos nor shell structures are preserved.

The Late Triassic-Early Jurassic Elliot Formation of South Africa's Karoo Basin has produced numerous Dinosaur egg fossils with embryos, as well as the skeletal remains of many non-Mammalian Cynodonts, something which has led to questions about whether Permo-Triassic Synapsids laid eggs at all. This is a serious consideration; Synapsids, particularly groups such as Lystrosaurus and Diictodon, are extremely common in the Permian and Triassic of the Karoo, with perinate specimens (specimens thought to have died around the time of birth or hatching) being found here and elsewhere, but no eggs are known. The preservation of Dinosaur eggs in the Karoo suggests there was no taphonomic process here producing a bias against the preservation of eggs, and palaeontologists have been active in the Karoo Basin for over 180 years, suggesting that if such eggs were present, there should have been a good chance of their being found. Egg-laying and bearing live young are found in closely related Snakes and Lizards, and it appears that this group has been able to switch back-and-forth between these conditions fairly easily. It is therefore conceivably possible that Synapsids developed the ability to bear live young very early in their history, and that Monotremes have secondarily switched back to egg-laying.

However, this has wider implications than Synapsid palaeontology. Current theories on the origin of lactation in Mammals have been built on the assumption that this preceeded the switch to live-birth (largely because Monotremes produce both eggs and milk). It is now generally accepted that the purpose of lactation was not originally to feed the young, but rather started as skin secretions used to either moisturise the eggs, provide nutrients, protect them against fungi and bacterial infections, or for hormonal signalling through the egg membrane. Should it be found that the Synapsids from which Mammals evolved bore live young, then these theories would have to be abandoned.

In a paper published in the journal PLoS One on 9 April 2026, Julien Benoit of the Evolutionary Studies Institute at the University of the Witwatersrand, Vincent Fernandez of the European Synchrotron Radiation Facility, and Jennifer Botha of the Evolutionary Studies Institute and Centre of Excellence in Palaeosciences at the University of the Witwatersrand, describe three perinate specimens of the Dicynodont Synapsid Lystrosaurus from the Early Triassic of Xhariep Municipal District in Free State Province, South Africa, one of which appears to have been preserved within an egg.

The specimens examined are the three smallest specimens attributed to Lystrosaurus. They include BP/1/4011, an isolated skull measuring 43.0 mm, discovered by James Kitching in the upper Palingkloof Member of the Balfour Formation at Orangia on Tweefontein 508, BP/1/9332, an almost complete articulated skeleton with a skull length of 44.0 mm, discovered by Brandon Stuart in the upper Palingkloof Member of the Balfour Formation at Nooitgedacht 68 Farm near Spitskop, and NMQR 3636, a complete skeleton with a skull length of 34.5 mm, found by John Nyaphuli at Rheeboksfontein 5 Farm in 2008, probably from the upper Palingkloof Member of the Balfour Formation or the lower Katberg Formation.Each of these fossils was a scanned at the European Synchrotron Radiation Facility in Grenoble, France, with three dimensional models being reconstructed with the Avizo Software Package.

The isolated skull BP/1/4011 was described by Kitching as the smallest known skull attributed to Lystrosaurus in 1964, and attributed to either Lystrosaurus murrayi or Lystrosaurus curvatus by a study in 2006. Benoit et al. are more cautious, attributing it to Lystrosaurus sp. but suggesting it shows affinities to Lystrosaurus curvatus.

The first of the articulated skeletons, BP/1/9332, is considered to be an early juvenile of Lystrosaurus sp., with affinities to Lystrosaurus murrayi. It is preserved in a splayed out position, similar to that of most larger Lystrosaurus specimens from the Karoo Basin, with most bones perfectly articulated, and synchrotron images show that no loose elements are preserved in the surrounding matrix. It appears to be the most developmentally advanced of the three specimens, because its splenials are co-ossified at the mandibular symphysis, although its occipital and basicranial bones remain loose. From the splayed out position in which it was found, Benoit et al. determine that it had hatched before dying, probably moving some distance from its hatching site before death.

Photograph of BP/1/9332 in dorsal view. Benoit et al. (2026).

The final specimen, NMQR 3636, is also considered by Benoit et al. to be an early juvenile of Lystrosaurus sp., with affinities to Lystrosaurus murrayi. However, unlike BP/1/9332, this specimen is curled into a fetal position, consistent with having been within an egg at the time of death. It also appears to be the most developmentally immature of the specimens, lacking tusk buds in its maxillary alveolae, something present in both the other specimens, or a mesethmoid bone, the structure that supports the olfactory bulbs in life, which is again present in the other two specimens. 

Most notably, the lower jaw of NMQR 3636 has an incompletely co-ossified symphyseal suture between the two paired bones in the lower jaw. This is completely co-ossified in both the other specimens, as well as in modern beaked Amniotes such as Turtles and Birds at the time of hatching. Modern Monotremes do hatch with an unfinished intermandibular symphysis, but these feed on milk provided by their mothers for some time after hatching, something Lystrosaurus is not thought likely to have been able to produce. 

Based upon this, Benoit et al. conclude that the early developmental stage of the skeleton, combined with a posture which would be expected of a perinate prior to hatching and a jaw which had not developed to the stage where it could feed on the hard foodstuffs likely to have been consumed by juvenile Lystrosaurus. is indicative of an Animal which died within the egg and was subsequently preserved, albeit without preservation of the egg itself.

Specimen NMQR 3636 in left lateral view. (a) Photograph of the specimen; (b) 3D digital reconstruction of the segmented bones; (c) live reconstruction by artist Sophie Vrard. Colour code for (b): vertebral elements in shades of green, ribs in blue, forelimb elements in red, femur in yellow, pelvic girdle elements in grey, skull in light red, mandible in light orange. Benoit et al. (2026).

Based upon the position of the embryo, it is estimated that the original egg was 3.65 cm long and 2.75 cm in diameter, with an internal mass of 115 cm³ and a mass of 115 g. While size estimates for adult Lystrosaurus vary, this is clearly larger compared to the size of an adult than either living Monotremes or most non-Avian Reptiles, although comparatively smaller than the eggs of Birds. This is probably indicative of a large yolk, which can feed the embryonic Animal for longer, allowing it to develop further within the egg. 

Modern Monotremes produce small eggs compared to the size of an adult, which contain comparatively little yolk material. This is possible because the young hatch at an early developmental stage, and are then nourished with milk. Interestingly, the Jurassic Tritylodontid Cynodont Kayentatherium produced eggs which were even smaller compared to the size of an adult. While Kayentatherium has been reconstructed as being quite Reptile-like in physiology, the small egg size could be a sign that it was capable of a form of lactation. It has also been suggested that Kayentatherium probably had hair, something which is known to be linked genetically to the formation of mammary glands (which produce milk), and it has also been shown that there is a genetic link between the reduction in egg yolk production and the ability to produce milk. All of which suggests that Kayentatherium may have been more Mammal-like than previously reconstructed, and that the appearance of the ability to produce milk may have been closely linked to the emergence of the Mammaliamorpha.

See also...

Evidence of seasonal torpor in an Early Triassic Antarctic Lystrosaurus.

Antarctica is today the coldest and driest continent with extreme variation in light availability throughout the year, restricting vertebrate life to coastal regions and rendering most of the continent uninhabitable. These modern environmental conditions are anomalous, however, considering the deep history of life in Antarctica when flora and fauna occupied large regions of the continent. Although more habitable with a warmer climate than today, Antarctica remained at a high latitudinal position for much of the Phanerozoic, subjecting its inhabitants to extreme photoperiod seasonality. Extant Vertebrates living in highly seasonally variable climates have evolved a variety of mechanisms to curb the effects of regular intervals of stress including daily torpor, hibernation, and brumation. These adaptations are largely behavioral thus rendering them difficult to study directly in the fossil record. Importantly, however, these adaptations reflect underlying metabolic changes in response to resource limitations, and therefore should be recognisable in fossil hard tissues that preserve chronological records of physiology.

Geological data from the Early Triassic document prolonged and unfavorable environments following the Permo-Triassic mass extinction. Permo-Triassic mass extinction survivors and newly evolved species would have had to adapt to high global temperatures, oceanic anoxia, and low nutrient availability that created unstable and highly variable environmental conditions. Polar regions are thought to have shielded their inhabitants from the extremes of these conditions both during the Permo-Triassic mass extinction and subsequently in recovery. The Fremouw Formation of Antarctica provides some of the earliest records of terrestrial Vertebrates of Early to Middle Triassic age (roughly 250–230 million years old). Furthermore, the flora and fauna of the Fremouw Formation is taxonomically similar to those found in non-polar regions of southern Pangaea, especially the Karoo Basin of South Africa, facilitating direct comparisons of polar and nonpolar populations.

In a paper published in the journal Communications Biology on 27 August 2020, Megan Whitney of the Museum of Comparative Zoology at Harvard University, and Christian Sidor of the Department of Biology and Burke Museum at the University of Washington, compare the frequency and patterns of growth marks in tusks of the Early Triassic non-Mammalian Synapsid Lystrosaurus, from polar Antarctica to those from the non-polar Karoo Basin of South Africa.

Dentine, a major tissue of the Vertebrate dentition, is deposited during times of regular incremental growth as well as times of arrested growth reflecting metabolic stress. Compared to bone or enamel, dentine acts as a particularly sensitive recorder of daily-to-monthly physiological activity providing a robust chronology of both regular and stressed growth and has previously been used to assess responses to environmental change. Despite this, the lack of sufficient experimental data on dentine deposition in extant Tetrapods makes specifying the absolute amounts of time recorded by each growth mark (i.e. daily growth, yearly growth, etc.) difficult. Instead, Whitney and Sidor adopt an agnostic terminology reflective of growth patterns where fine-scale, regular marks denote baseline or routine growth and thicker more pronounced growth marks are referred to as stress marks.

 

Measurements for stress and regular growth were recorded from the tusks of Lystrosaurus. (a) A cross-section of Antarctic specimen UWBM 118025 with a 'hibernation zone' highlighted at a higher magnification. Scale bars are 1000 μm. (b) Well-preserved regular incremental growth marks from the South African specimen UWBM 118028, lacking 'hibernation zones'. Arrows denote individual lines with an average spacing of 16–20 μm. Scale bar is 100 μm. Whitney & Sidor (2020).

The tusks of Lystrosaurus serve as particularly extensive markers of seasonality because they have been shown to be evergrowing. Such tusks can therefore capture extended periods of time and control for the developmental stage of the tooth, reducing any bias toward rapid growth in newly erupted teeth. Furthermore, ever-growing dentitions such as incisors of modern Rodents are known to preserve evidence of seasonal stress and hibernation as well as in fossil Rodents and the tusks of Mammoths. Previous descriptions of a 'hibernation zone' in these dentitions are recorded as episodes of shortened intervals between stress lines and as such, we accordingly employ these characteristics in testing for torpor in our Early Triassic sample.

Whitney and Sidor found evidence of prolonged and repeated metabolic stress events in the tusks of Antarctic Lystrosaurus that differ from the relatively steady growth observed in South African Lystrosaurus tusks. The patterns of stress found in polar Lystrosaurus are similar to previously described 'hibernation zones' suggesting that Antarctic Lystrosaurus experienced seasonal torpor, likely similar to hibernation. This preliminary finding supports the growing body of evidence that Lystrosaurus was endothermic and highlights the role of polar regions in the recovery of terrestrial vertebrates from the Permo-Triassic mass extinction.

Whitney and Sidor found that the spaces between regular, incremental growth marks in the tusks of Antarctic Lystrosaurus were not significantly different from those of South African Lystrosaurus indicating that although geographically separated by over 900 km in the Triassic, the baseline physiology and growth was generally similar in both populations and across individuals in our sample. These baseline indicators of physiology allowed Whitney and Sidor to control for alternative sources of variation in growth patterns between the two populations (i.e. differences in growth rate due to ontogeny or species/individual variance). In modern ever-growing dentitions, these regular growth marks have been demonstrated to vary with factors such as age, species of varying metabolisms, and dentine deposition is sensitive to nutrient inputs. Completely controlling for alternative sources of variation was particularly difficult given the small and fragmentary nature of the specimens that were available for destructive sampling, however, Whitney and Sidor consider these regular growth marks to be at least a general control for those sources of variation in growth that are unrelated to seasonality.

 

Stress and regular incremental data for Antarctic (blue) and South African (orange) Lystrosaurus tusks. (a) The mean distance between regular incremental growth marks was insignificantly different between the two populations suggesting similar baseline metabolic activity in Antarctic and South African Lystrosaurus populations. (b) The distance between growth marks was significantly greater in South African specimens indicating longer durations of uninterrupted growth. (c) The thickness of stress lines in Antarctic specimens was significantly greater than South African specimens indicating longer periods of inactive growth. (d)–(f) Measurements averaged in (a)–(c) separated by data collected for each specimen. Considerable variation was observed, but even with outliers removed, the average significant differences remained consistent. Whitney & Sidor (2020).

While Whitney and Sidor's sample contained individuals of similar baseline metabolic activity, indicators of metabolic stress were different between Antarctic and South African specimens. Quantitatively, both the duration of stress and the short intervals between stressful events suggest that Antarctic Lystrosaurus experienced relatively frequent and pronounced metabolic strain. The amount of growth between stressful events was, on average, significantly greater in South African Lystrosaurus suggesting longer durations of regular growth without stressful interruptions for non-polar populations that inhabited the Karoo Basin. Furthermore, stressful events appear to have lasted for longer durations in Antarctic fossils as suggested by the significantly thicker lines observed in tusks from the Fremouw Formation. Antarctic tusks preserve stressed growth marks akin to previous descriptions of a 'hibernation zone' where a series of thick stress marks are found close to one another while South African specimens typically display a single stress mark followed by regular growth that constitutes the majority of the growth record of this population.

 

Summary of stress mark data from a selection of South African (orange) and Antarctic (blue) specimens of Lystrosaurus. These graphs represent transects collecting the thickness (μm) of stress lines moving from the pulp cavity (to left) to the outer edge of the tusks (to right). Green boxes highlight durations without visible stress lines and gray boxes highlight portions of the tusk with closely spaced stress lines suggesting a stressful interval. The height of the boxes represents the thickest stress line during such period. Whitney & Sidor (2020).

Substantial variation within localities does exist. However, even when outliers are removed from Whitney and Sidor's quantitative analyses, statistically significant differences in stress marker measures persist. In fact, this variation is an important consideration given that not every stress line necessarily represents torpor, even in the Antarctic populations. Short periods of metabolic reduction may be caused by a variety of factors, but the unique patterns here observed in Antarctic tusks, where occurrences of closely spaced stress lines are present, are consistent with torpor at high latitudes.

 

Comparative measurements of stress lines in Antarctic (blue) and South African (orange) tusks. There is substantial variability within each population, however, South African stress lines tend to be thinner and farther apart than Antarctic specimens which are more likely to occur closer together and more frequently. This is apparent as individual data points (a) and when specimens are assigned a mean value for these measurements (b). Whitney & Sidor (2020).

From their exploratory study, Whitney and Sidor find evidence of severe and prolonged periods of stress in Antarctic Lystrosaurus tusks that support the conclusion that polar populations adapted to their high-latitude environment by means of seasonal reduction in metabolic activity, otherwise referred to as torpor. The 'hibernation zones' denoted here by temporarily reduced dentine deposition between stress lines are quantitatively and qualitatively akin to heterothermic activity observed in modern endotherms. Heterothermic ectotherms reduce their metabolic activity from at least half of to nearly complete quiescent metabolic activity. Heterothermic endotherms, on the other hand, can enter a state of torpor generally reducing metabolic activity by at most a third although most reduce by no more than 10% of normal activity. Generally, ectothermic heterotherms are not able to reactivate metabolic activity during unfavorable environmental conditions and enter times of brumation whereas endothermic heterotherms, even hibernators, frequently will come out of metabolic dormancy either daily, weekly, or monthly. The zones of stress observed here in Antarctic Lystrosaurus are marked by iterative reactivation of metabolic activity similar to those seen in torpor patterns of modern endotherms. This contributes additional support for a growing body of evidence that Dicynodonts like Lystrosaurus were likely endothermic.

These data also shed light on Antarctica’s role as a refugium during the Permo-Triassic mass extinction. Antarctic rocks have yielded Early Triassic Tetrapod taxa that are missing from other contemporaneous, but otherwise much better sampled localities such as the Karoo Basin of South Africa. These discrepancies in otherwise very similar faunal assemblages, have supported the hypothesis that the Antarctic portion of Pangaea was a high-latitude refugium from the global climatic events marked by the Permo-Triassic mass extinction. Furthermore, geologic data suggest that polar regions were, in fact, the first to begin a prolonged recovery in the Early Triassic. With its relatively temperate climate, Antarctica may have acted as a haven for terrestrial vertebrates through an extinction boundary and subsequent recovery.

Although more insulated from the effects of global climate change, tetrapods living in Antarctica during the Early Triassic would have had to adapt to extreme seasonality with long periods of limited light availability. A Permian Tetrapod assemblage has yet to be recorded from Antarctica, however, Lystrosaurus tusks from both the Permian and Triassic of the Karoo Basin do not record patterns of hibernation-like reductions in their metabolic activity. Thus, these data suggest that upon expanding its geographic range to the Antarctic portion of southern Pangaea Lystrosaurus adapted with extended periods of reduced metabolic activity, although continued testing of this initial observation is required.

Lystrosaurus survivorship through the Permo-Triassic mass extinction and its subsequent abundance in the fossil record of the earliest Triassic was likely predicated on a flexible physiology that could modulate typically elevated metabolic activity according to the limiting resources of a fluctuating environment. This agrees with James Valentine's suggestion that more stable environments tend to select for narrow niche partitioning among species, whereas those with unstable resources, such the Early Triassic, tend to select for species with greater flexibility and generalisation. Indeed, the near-global distribution of Lystrosaurus, with records known from China, Russia, India, Africa, and Antarctica, implies a remarkable ecological breadth for this lineage. Furthermore, Triassic rocks from both South Africa and Antarctica preserve fossil evidence of tetrapod burrowing, including for Lystrosaurus. Whitney and Sidor suggest that a combination of a flexible physiology and burrowing served as exaptations to the acquisition of torpor for Antarctic populations of Lystrosaurus.

Whitney and Sidor show preliminary evidence that Lystrosaurus used torpor to respond to the seasonal stress incurred specifically in the polar regions of southern Pangaea during the Early Triassic. It was this ability to sustain activity in a variety of stressful environmental conditions that may have served as a critical adaptation in surviving and recovering from the largest mass extinction the Earth has experienced to date. The Fremouw Formation preserves a diverse assemblage of tetrapod taxa with presumably an array of metabolic adaptations to the extremes of seasonal light availability. Continued testing of seasonal responses in Lystrosaurus, other non-Mammalian Synapsids, early Reptiles, and the abundant Temnospondyl fossils recovered from these localities can reveal how this polar ecosystem evolved despite unstable environmental conditions and eventually facilitated postextinction recovery.

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Previously unidentified Burnetiamorph specimens from the Permian Karoo Basin of South Africa,

The Burnetiamorphs are a poorly understood group of Permian Theraspids (Theraspids are the group which gave rise to and and include the living Mammals, though Burnetiamorphs are not thought to be particularly closely related to the earliest Mammals or their direct ancestors) known from Southern and East Africa and Russia. The group has a somewhat limited fossil record; by the end of the twentieth century only two species had been described, one from South Africa and one from Russia, though since then the number has risen to ten species. The most commonly preserved part of Burnetiamorphs is a heavy bone boss, made up of the fused and thickened bones of the occipital region and the upper part of the braincase, though it is often hard to identify the different bone components in these dense structures, making them of limited use for understanding relationships within the group.

  

In a paper published in the journal Palaeontologia Africana on 23 March 2016, Christian Kammerer of the Museum für Naturkunde at the Leibniz-Institut für Evolutions- und Biodiversitätsforschung and the Evolutionary Studies Institute at the University of theWitwatersrand, records two previously undescribed Burnetiamorph specimens from museum collections. Both specimens originate in the Karoo Basin of South Africa, and both are considered by Kammerer to be too fragmentary to assign to a species, but they nevertheless provide insights into this little known group.

The first specimen described, TM 4305, comes from the collection of the Ditsong National Museum of Natural History in Pretoria. It comprises a weathered and only particularly prepared skull fragment, including the interorbital region, temporal region and dorsal occiput. Any details of where or when, or by whom this specimen was collected appear to have been lost, though it does have a label attached, identifying it as coming from the Tapinocephalus Assemblage Zone, making it Middle Permian in age.

TM 4305 in (A) right lateral, (B) left lateral, (C) anterior, (D) ventral and (E) posterior views. nb, Nasal boss; or, orbit; po, postorbital bar; sb, supraorbital boss; sp, sphenoid element; tf, temporal fenestra. Kammerer (2016).

The second specimen described, NHMUK R871, comes from the collection of the Natural History Museum in London. This specimen comes with more detailed location information, having been collected by palaeontologist Thomas Bain (1797-1864) at a site in Tafelberg, Beaufort West, which produced a number of other, more complete and more studied, vertebrate fossils, all of which were assigned to the genus Tropidostoma; the location is therefore considered to be part of the Tropidostoma Assemblage Zone, making it Late Permian in age.

This specimen comprises a fragment of skull roof preserving the interorbital region and temporal roof to the anterior edge of the pineal foramen. It was originally identified as a 'Theriodont? Reptile' and subsequently as a 'Deinocephalian', but both a Deinocephalian in the Tropidostoma Assemblage Zone and a Theriodont with the extent of bone fusion and thickening seen in the specimen are highly unlikely. The pattern of bone fusion is, however, consistent with a Burnetiamorph, and Kammerer feels confident in assigning the specimen to this group.

NHMUK R871 in (A) right lateral, (B) left lateral, (C) anterior and (D) posterior views. mb, Median boss; sb, supraorbital boss. Kammerer (2016).

See also...

Dinocephalian Therapsids from the Middle Permian of the Karoo Basin, South Africa.       The Dinocephalians were a group of mostly large, herbivorous Therapsids (the group that also includes Dicnodonts and Mammals) known from the Middle Permian of Russia, Central Asia, China...

Scavenging on the body of a Dicynodont Therapsid in the Late Permian of the Karoo Basin.                                                     Therapsids were a group of Synapsid Amniotes (the group of terrestrial vertebrates that include the...

Strange bedfellows in an Early Triassic burrow from the Karoo.                                              The Early Triassic Karoo Basin contain numerous preserved burrows of small Tetrapods, interpreted as adaptations to a harsh, seasonally dry, climate...

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Dinocephalian Therapsids from the Middle Permian of the Karoo Basin, South Africa.

The Dinocephalians were a group of mostly large, herbivorous Therapsids (the group that also includes Dicnodonts and Mammals) known from the Middle Permian of Russia, Central Asia, China, Brazil, Tanzania, Zambia, Zimbabwe and South Africa, that briefly formed a dominant part of terrestrial faunas before becoming abruptly extinct. Their sudden rise to dominance and equally sudden disappearance has led to them being used to help define the fossil biozones (stratigraphic time periods defined from fossil assemblages – these are generally defined using pollen in later terrestrial settings, but no pollen was present in the Permian) used to date terrestrial sediments from South Africa, and since these South African rocks have a number of volcanic horizons used to obtain isotopic dates for these biozones, they in turn are considered a global reference point for dating events in early Tetrapod evolution. Dinocephalian Therapsids first appear in the Eodicynodon Biozone, then rise to become a diverse and dominant part of the fauna in the Tapinocephalus Biozone, but are absent from the overlying Pristerognathus Biozone; there disappearance is therefore one of the factors used to define the boundary between the Tapinocephalus and Pristerognathus Biozones.

In a paper published in the South African Journal of Science on 27 March 2015, Michael Day, Saniye Güven, Fernando Abdala, Sifelani Jirah and Bruce Rubidge of the Evolutionary Studies Institute at the School of Geosciences at the University of the Witwatersrand and John Almond of Natura Viva in Cape Town describe two new Dinocephalian specimens from the lower Poortjie Member of the Teekloof Formation in the Beaufort West District of Western Cape Province, South Africa.

Both of the new specimens comprise the rear portions of skulls, and both are assigned to the genus Criocephalosaurus, of which two species have previously been described. However since both of these species were described from cranial roofs only, with Criocephalosaurus vanderbyli described from a single weathered cranial roof and Criocephalosaurus gunyankaensis described from four cranial roofs, all of which are currently missing, the new specimens are not assigned to species level. They are notably smaller and more slender than other specimens assigned to the genus, but it is unclear based upon the available material whether they are members of a new species or juveniles of one of the previously described species.

Photos of the specimens (a–d) SAM-PK-K10888 and (e–g) BP/1/7214 showing (a,e) dorsal view, (b,f) left lateral view, (c,g) right lateral view and (d) occipital view. (h) View of sagittal plane on right posterior part of the skull of SAM-PK-K10888, showing the pineal canal orientated parallel to the occipital plane. (i, j) Idealised skull of Criocephalosaurus showing the portions preserved in (i) BP/1/7214 and (j) SAM-PK-K10888. Day et al. (2015).

The boundary between the Tapinocephalus and Pristerognathus Biozones has previously been placed in the upper part of the Abrahamskraal Formation, with the boundary between the Abrahamskraal and Teekloof Formations within the Pristerognathus Biozone. The discovery of specimens of Criocephalosaurus within the lower Poortjie Member of the Teekloof Formation suggests that this scenario is wrong, and that either the boundary between the Abrahamskraal and Teekloof Formations lies within the Tapinocephalus Biozone or Criocephalosaurus extends into the Pristerognathus Biozone. This adds to a growing problem defining the boundary betweem the two biozones, with specimens of the two fossil groups considered diagnostic of the Pristerognathus Biozone, Diictodon and Pristerognathus, having recently been discovered within the Tapinocephalus Biozone, and Day et al. suggest that these biostratigraphical units need reviewing in the near future.

(a) Extension of the Tapinocephalus Assemblage Zone (AZ) into the lower Teekloof Formation. Arrows indicate the extension of Tapinocephalus AZ into the Teekloof Formation. (b) Stratigraphic section measured at Beaufort West between the level of the SAM-PK-K10888 locality and the lower Hoedemaker Member. (c) Stratigraphic section on the farm Putfontein. Day et al. (2015).

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Kannemeyeriiforme Dicynodonts from the Middle Triassic of Shanxi Province, China.

Triassic deposits are widespread in Northern China, but Tetrapod fossil producing locations are very rare. Those that are known are restricted to the Heshanggou, Ermaying and Tongchuan...

Scavenging on the body of a Dicynodont Therapsid in the Late Permian of the Karoo Basin. 

Therapsids were a group of Synapsid Amniotes (the group of terrestrial vertebrates that include the...

A Caseid Synapsid from the Late Pennsylvanian of Kansas.

Synapsids, the group which gave rise to and includes the modern Mammals (and which are sometimes misleadingly known as ‘Mammal-like Reptiles’) diverged from the other early Amniotes (fully terrestrial Vertebrates) about 315 million years ago in the Late Carboniferous, and went on to become the dominant large vertebrates in Permian ecosystems, though they suffered badly in the end-Permian extinction, and... 

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Scavenging on the body of a Dicynodont Therapsid in the Late Permian of the Karoo Basin.

Therapsids were a group of Synapsid Amniotes (the group of terrestrial vertebrates that include the modern Mammals which are sometimes, misleadingly, known as ‘Mammal-like Reptiles), that reached great diversity in terrestrial ecosystems throughout Pangea (the ancient supercontinent of the time, which included all the modern continents joined together) in the Permian and Triassic, before being  largely replaced by more successful Archosaur groups, notably the Dinosaurs and Crocodylomprphs. The group is particularly well known from the Karoo Basin of South Africa.

In a paper published in the South African Journal of Science on 29 October 2012, Nicholas Fordyce of the Department of Zoology at the University of Cape Town, Roger Smith of the Iziko South African Museum in Cape Town and Anusuya Chinsamy, also of the Department of Zoology at the University of Cape Town, describe evidence of scavenging on the body of a Dicynodont Therapsid (a group of herbivorous Theraspids which often reached large sizes that had both beaks and tusks, and which may have survived as late as the Cretaceous) from mudrocks of the Tropidostoma Assemblage Zone of the Late Permian Beaufort Group, near Loxton in Northern Cape Province by John Nyaphuli in 1984, and prepared at the Iziko South African Museum in Cape Town by Annelise Crean. It has never been formally described and named, but is affectionately known as ‘Mamafura’.

The partially articulated Dicynodont ‘Mamafura’; the arrow indicates the left femur. Fordyce et al. (2012).

The skeleton of ‘Mamafura’ has articulated foreparts, but the hindquarters are more-or-less totally disarticulated. The bones show a level of weathering that is consistent with about two years spent exposed on the surface prior to complete burial. Sedimentary evidence suggests they originally lay on a semi-arid floodplain, and underwent three or four flood events before being finally buried, during which time some of the smaller bones of the animals feet were lost, either to water transportation or scavenging.

The left tibia of ‘Mamafura’ has two elongate grooves, which are thought to be the result of the actions of a scavenging or predatory animal. There is also a single circular indentation, 18 mm in diameter, on the left femur. 

(b and c) A large spherical puncture on the left femur, and (d) tooth scratch marks on the left tibia of ‘Mamafura’. Fordyce et al. (2012).

A broken canine tooth, 3.5 cm in length, was found with the skeleton. This has distinctive serrations on its lateral margins. Two Therapsid groups present in the fauna of the Karoo basin at the time of ‘Mamafura’ could produce a canine tooth of this size, the Therocephalians and Gorgonopsians, but no known Therocephalian has the sort of serrations seen on the tooth, suggesting that it came from a Gorgonopsian, probably Aelurognathus or possibly Cyonosaurus.

(a) The unidentified canine associated with the Dicynodont skeleton and (b) its serrations. (c) A Cyonosaurus specimen and (d) the 0.2-mm long serrations on the canine of Cyonosaurus and (e) an Aelurognathus specimen. (f) A silicon cast showing details of the serrations on a canine of Aelurognathus. Note the square serrations of (b) and (f) compared to the somewhat more rectangular serrations in (d). Fordyce et al. (2012).

Fordyce et al. suggest that soon after death ‘Mamafura’ was scavenged by a pack of Aelurognathus, acting in a similar way to modern Canids (Dogs). These preferentially attacked the rear and underbelly of the corpse, disarticulating the bones of the hindquarters, but not opening the ribs. Neither Aelurognathus nor Cyonosaurus appears to have been well adapted for durophagy (crushing bones or other hard foods), so it is doubtful that capable of making the marks found on the bones of the left hindlimb of ‘Mamafura’. Fordyce et al. suggest that these marks were either made by some other, unidentified, predator, possibly the animal responsible for the initial kill, or are the result of some other taphonomic process (post-mortem bone modification) that resembles tooth damage.

See also….

 A Caseid Synapsid from the Late Pennsylvanian of Kansas.









 Strange bedfellows in an Early Triassic burrow from the Karoo.

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Strange bedfellows in an Early Triassic burrow from the Karoo.

The Early Triassic Karoo Basin contain numerous preserved burrows of small Tetrapods, interpreted as adaptations to a harsh, seasonally dry, climate. These burrows are commonly preserved as casts, formed when the burrow was infilled with sediment different to the surrounding matrix, typically during flood events, and these casts sometimes contain the preserved remains of the animals that lived in the burrows.

In a paper published in the journal PLoS One on 21 June 2013, a team of scientists led by Vincent Fernandez of the Evolutionary Studies Institute at the University of the Witwatersrand describe the results of an examination of one such burrow cast, collected from the lower Lystrosaurus Assemblage Zone on Admiralty Estates at the base of Oliviershoek Pass in KwaZulu Natal Province, South Africa, at the European Synchrotron Radiation Facility, where it was possible to create a three dimensional computer model of the contents of the cast without breaking it open.

The burrow cast contains two preserved animals from completely different groups, a Cynodont ('Mammal-like Reptile'), Thrinaxodon liorhinus, and a Rhinesuchid Amphibian, Broomistega putterilli. Both skeletons are articulated, suggesting that neither was being predated by the other at the time of death (predation generally involves dismembering the prey animal). The Amphibian shows damage to several ribs, as well as a bite mark on the skull, however the ribs show signs of healing prior to death and the bite-make is inconsistent with the dentition of the Cynodont.

Upper-side 3D rendering of the content inside the burrow cast in semi-transparency. Thrinaxodon liorhinus (in brown) is lying on its ventral side; Broomistega putterilli (in grey) deposited upside down on the right side of the Thrinaxodon. Fernandez et al. (2013).

The two animals are preserved in a position that almost suggests they are hugging, but Fernandez et al. suggest this is probably a post-mortem positioning; the burrow filled with water in a flood event drowning the animals, and almost certainly repositioning them, though since the burrow has a narrow entrance it is unlikely that either animal was washed into it. They suggest that the burrow was dug by the Cynodont, as the Amphibian seems poorly adapted to the task and Cynodonts are well documented in similar burrows. They further suggest that the Amphibian entered the burrow after sustaining its injuries, possibly to escape from a predator, and that the Cynodont tolerated this presence, possibly because it was aestivating (dormant, hibernating). This leads them to suggest that the Cynodont may have become dormant during the driest part of the year, and that both animals died as a result of flash flooding at the onset of the rainy season.

See also Stomach contents in Jurassic Salamanders, The first Dinosaur? An immature Temnospondyl Amphibian from the Late Triassic of Brazil, A Flying Fish from the Middle Triassic of Guizhou Province, China and A predatory Archosaur from the Late Triassic of southern Poland.

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