Thursday, 14 November 2019

Caridina biyiga: A new species of Freshwater Shrimp from Leichhardt Springs, in the Kakadu National Park of Australia's Northern Territory.

Freshwater Shrimps of the genus Caridina are widely distributed in tropical and subtropical waters across Africa, Asia, Australia and Oceania. They are omnivores, able to consume a wide variety of foodstuffs, but often have very specific environmental tolerances, which results in a large number of species, most of which have very limited distributions. The genus was first reported in the Northern Territory in 1967, and the area is known to be home to a number of undescribed species.

In a paper published in the journal Zootaxa on 6 November 2019, John Short of BioAccess Australia, Timothy Page of the Australian Rivers Institute at Griffith University, and Christopher Humphrey of the Heritage, Reef and Marine Division of the Department of Environment & Energy, describe a new species of Caridina from the Leichhardt Springs hydrothermal system in the Kakadu National Park of Australia's Northern Territory.

Leichhardt Springs has two dominant outflows approximately 320 m apart, a north arm and a south arm, with a downstream confluence into the northern branch of Burdulba Creek. The heat source of Leichhardt Springs is presently undetermined although other thermal springs in the Alligator Rivers Region (including western Arnhem Land) are known to be associated with high heat-producing rocks in the basement of the crust. No other thermal springs are presently known from Kakadu National Park.

The thermal properties of Leichhardt Springs were investigated over a four to five-month period during the 2014 winter-spring dry season using two CTD-Diver multi-parameter dataloggers deployed on the north arm of Leichhardt Springs, one at the head of the spring and the other 160 m downstream. A third Diver was also deployed in Radon Springs, a non-thermal spring located approx. 6 km to the northeast on the large, outlying, sandstone formation above Leichhardt Springs (Fig. 1). Over the five-month period, water temperature at the head of the north arm spring was an invariant 30.2°C and 160 m downstream, almost constant and only slightly cooler, at 29.2–30.3°C. By comparison, Radon Springs showed a much higher temperature range, 22.1–29.3°C, thus 1–8°C cooler over the same period. A sampling trip to the south arm of Leichhardt Springs in June 2016 revealed thermal properties similar to the north arm.

Apart from its thermal properties, the location of Leichhardt Springs relative to the Kakadu-Arnhem Land plateau and escarpment complex is also interesting. Other sandstone-formation springs in Kakadu National Park arise within small gorges and typically at the immediate base of escarpments. Leichhardt Springs is located approximately 900 m away from the western escarpment of an outlying sandstone formation and at a lower elevation.

Satellite imagery of Leichhardt Springs shows extensive rainforest vegetation along both arms associated with the permanent, spring-fed outflows. The head of the north arm outflows through a patch of small, abraded and bleached, sandstone cobbles. For at least 300 m downstream, the north arm is characterised by a sequence of pools with clean, quartzite sand substrate interspersed with swift-flowing runs and riffles of gravel and cobble. Riparian trees include Melaleuca spp. (Paperbarks), Carallia brachiata (Corkwood), Pandanus aquaticus (Pandan), Canarium australianum (Mango Bark), Syzygium spp.(Lillipillies), and the monsoon rainforest-specific species, Nauclea orientalis (Yellow Cheesewood), and Melicope elleryana (Pink Flowered Doughwood). The understorey comprises climbing Vines, Flagellaria indica (Whip Vine),  and Rhaphidophora australasica (Needle Berry), climbing Ferns, Stenochlaena palustris (Midin), groundstorey Ferns, Blechnum orientale (Oriental Blechnum) and the flowering shrub, Melastoma sp. (Melastomes). The macrophyte, Eleocharis sp. (Spikerush), is commonly interspersed amongst runs and riffles of the stream.

 Maps showing the location of the study area. Upper left, location of the general study area within Australia; upper right, detailed view of the study area showing the location of Leichhardt Springs; main lower map, broader view of the study area showing its location within Kakadu National Park and the Northern Territory. Short et al. (2019).

The new species is named Caridina biyiga, meaning meaning ‘different’ or ‘other’ in the indigenous Gundjeihmi language of the region, in reference to its unusual morphology compared to other species of Caridina. Although the general morphology of the new species is typical of Caridina, the arrangement of the limbs, fingertips of the chelae (claws) and fifth pereiopod dactylus (lower part of the fifth walking leg) are unusual for the genus. Caridina biyiga lacks an arthrobranch (gill) at the base of the first cheliped (claws) and has 8 pairs of branchiae (gills) rather than the full complement of 9 branchiae normally associated with Caridina. There is also a vestigial epipod (projection) on the first maxilliped (mouthpart).

Caridina biyiga, female. Scale bar is 0.2 mm. Short et al. (2019).

Caridina biyiga is a small, subcylindrical, rotund species for the genus. Maximum size of females 3.05 mm in length; males 2.15 mm in length); minimum size of breeding females 2.15 mm long. The species is translucent with rust brown chromatophores (colour cells). Chromatophores either small and widely spaced giving speckled appearance or forming large blotches, blotches tending to be grouped as transverse bands on abdomen and posterodorsal carapace, widely spaced on ventral carapace and pereiopods, closely spaced on anterodorsal carapace.

(A)–(B) Live colouration of Caridina biyiga (photos by Dave Wilson); (C) south arm of Leichhardt Springs, riffle near head of spring (photo by Michael Hammer); (D) aerial view of Leichhardt Springs (heavily vegetated area in foreground) (photo by Michael Hammer); (E) North arm of Leichhardt Springs, type locality of Caridina biyiga, riffle near head of spring (photo by Michael Hammer). Short et al. (2019).

See also...
Follow Sciency Thoughts on Facebook.

Tuesday, 12 November 2019

Mexican miner killed in rockfall.

A miner has died at the San Ignacio gold and silver mine in Guanajuato State, Mexico. Jesus Demetrio Ramirez Bueno, 41, died at the Great Panther Mining-owned site on the afternoon of Friday 8 November 2019. The incident is understood to have happened on an access ramp, rather than on an area of active excavation, with the area where it happened being closed while an investigation is carried out. Mining operations at the site are apparently not effected, with production continuing while the investigation is ongoing.

Mining operations at the San Ignacio mine. Great Panther Mining.

The San Ignacio mine forms part of the Guanajuato Mine Complex, which targets gold and silver precipitated in veins along faults in  a Palaeocene to Pliocene sequence of dacite-rhyolite, andesite and basalt, known as the  La Luz Vein System. These veins run north-south across the area, and predominantly contain calcite and silica, with precious metals concentrated along three main belts, the La Luz, Veta Madre and Sierra vein systems. The San Iguacio Mine is located on the La Luz Vein System.

Location map of the Guanajuato Mining District, Mexico, showing the Veta Madre, La Luz and Sierra vein systems, along with historic and recent mines. An enlargement showing veins and mines on the La Luz system is shown on the left. Moncada et al. (2017).

See also...
Follow Sciency Thoughts on Facebook.

Magnitude 4.9 Earthquake in the Ardèche Department of southern France injures four.

The Centre Sismologique Euro-Méditerranéen recorded a Magnitude 4.9 Earthquake at a depth of 10 km, in the Ardèche Department of western France, slightly after 11.50 am local time (slightly after 10.50 am GMT) on Monday 11 November 2019. The Earthquake is reported to have reported in four injuries and minor damage to several buildings. One of the injured people is described as being in a serous condition after being hit by falling scaffolding in Montélimar; the other three injuries were more minor and caused by panic rather as a direct result of the Earthquake.

The approximate location of the 11 November 2019 Ardèche Department Earthquake. Centre Seismologique Euro-Méditeranéen.

The precise cause of Earthquakes in France can be hard to determine; the country is not close to any obvious single cause of such activity such as a plate margin, but is subject to tectonic pressures from several different sources, with most quakes probably being the result of the interplay between these forces.

France is being pushed to the east by the expansion of the Atlantic Ocean and to the north by the impact of Africa into Europe from the south. It is also affected by lesser areas of tectonic spreading beneath the North Sea, Rhine Valley and Bay of Biscay. Finally the country is subject to glacial rebound; until about 10 000 years ago much of the mountainous and upland areas of the country were covered by a thick layer of glacial ice, pushing the rocks of the French lithosphere down into the underlying mantle. This ice is now gone, and the rocks are springing (slowly) back into their original position, causing the occasional Earthquake in the process. 

Glacial rebound seems an unlikely cause of Earthquakes in the Channel region, an area that was never glaciated, but this is not entirely the case. The northwest of Scotland is rising up faster than any other part of the UK, but the Earth's crust on land in the UK is fairly thick, and does not bend particularly freely, whereas the crust beneath the Channel is comparatively thin and more inclined to bend under stress. Thus uplift in Scotland can cause the entire landmass of Great Britain to pivot, causing movement in the rocks beneath the Channel, and affecting both the English and French coasts.

(Top) Simplified diagram showing principle of glacial rebound. (Bottom) The extent of glaciation in Europe at the last glacial maximum. Wikipedia.

Witness accounts of Earthquakes can help geologists to understand these events, and the structures that cause them. The Centre Seismologique Euro-Méditeranéen is interested in hearing from people who may have felt this event; if you felt this quake then you can report it to them here.
See also...
Follow Sciency Thoughts on Facebook.

Monday, 11 November 2019

Aquilarhinus palimentus: A new species of Hadrosaurid Dinosaur from the Late Cretaceous of Big Bend National Park, south-western Texas.

Hadrosaurs, or Duck-Billed Dinosaurs, were large herbivorous Ornithischian Dinosaurs widespread across Laurasia (Eurasia plus North America; Laurasia split away from the southern continents in the Triassic, the split into North America and Eurasia during the Cretaceous) as well as South America and Antarctica during the Late Cretaceous. They were descended from the earlier Iguanadontids, but with more sophisticated jaws and teeth, which allowed them to chew their food, not by side-to-side motion as in a modern mammal, but by a unique flexion of the upper jaw parts, which moved apart as the lower jaw moved upwards. The term 'Hadrosauroid' refers to the widest possible grouping of Hadrosaurs, including all animals in the group after their evolutionary split with the Iguanadontids in the Early Cretaceous, whereas the term 'Hadrosaurid' refers to the most derived members of the group, which appeared in the Late Cretaceous and are split into two subgroups, the Lambeosaurs, which had hollow bony crests, thought to have been used for making sounds, and the Saurolophides, or Hadrosaurines, which either lacked crests or had solid ones.
In a paper published in the Journal of Systematic Palaeontology on 12 July 2019, Albert Prieto-Marquez of the Institut Catal a de Paleontologia Miquel Crusafont at the Universitat Aut onoma de Barcelona, and the Museu de la Conca Dell a-Parc Cretaci, and Jonathan Wagner and Thomas Lehman of the Departament of Geosciences at Texas Tech University, describe a new species of Hadrosaurid Dinosaur from the Late Cretaceous Aguja Formation of Big Bend National Park, south-western Texas.

The Aguja Formation of western Texas preserves one of the southernmost Campanian ( 83.6  to 72.1 million years old) terrestrial vertebrate faunas in North America. Nearly the entire fauna, however, is known from the uppermost part of the formation (the upper shale member). Until recently, very little was known about the vertebrate fauna found in the lower part of the formation (the lower shale member). S diverse assemblage of small Theropod, Lizard and Mammal teeth (the ‘Lowerverse local fauna’) has been described from a single locality in the lower shale member, as has a more general fauna and stratigraphy, but otherwise the vertebrate fossils of the lower Aguja Formation remain undocumented.
Terrestrial and paralic strata of the Aguja Formation are widely exposed in and around Big Bend National Park in south-western Texas. These strata are underlain by and intertongue with marine deposits of the Pen Formation. The Aguja consists of two eastward-thinning intervals of terrestrial strata (the lower and upper shale members) separated by a westward-thinning wedge of interposed marine strata – the McKinney Springs tongue of the Pen Formation. The upper shale member is widely exposed throughout Big Bend National Park and surrounding areas, but the lower shale member is mostly exposed on private ranches west of the park; it thins and pinches out in the south-western part of the park and does not extend into the eastern portion.
The lower shale member of the Aguja Formation consists primarily of thick beds of lignitic clay-shale with several prominent sandstone and coal beds, particularly near the base. In the middle of the lower shale member there is a thin zone of interbedded very fine sandstone and carbonaceous mudstone with conspicuous iron-manganese concretions. This concretionary interval is the only part of the lower shale member that yields significant vertebrate fossils, and the holotype specimen of the new Hadrosaurid documented here was collected from these strata. 
The lower shale member is interpreted as having accumulated primarily in a coastal swamp or marsh environment. The specimen was recovered from within a bed of mudstone having irregular bedding planes covered with abundant large carbonised leaf and wood fragments, many of which are riddled with Teredolites borings. The bones are partially enclosed in large concretions of iron-manganese oxides. Some of the bones were broken prior to burial, but articulation surfaces are intact and the cortical surfaces exhibit little cracking, indicating that the bones had been subject to minimal transport or weathering prior to burial. Immediately overlying the bone-bearing bed is a thin layer with abundant small Ostreid Bivalve shells, but no other remains are preserved at the site.
The vertebrate fauna from the lower shale member dates back to between 81 and 80 million years ago, corresponding to the early Campanian. This fauna may be slightly older than that of the Wahweap Formation in Utah and lower Two Medicine Formation in Montana. Only a few Hadrosaurids have been described from these strata, such as Gryposaurus latidens and Acristavus gagslarsoni (both from the Two Medicine Formation of Montana) and these are among the oldest known Hadrosaurids. The new species from the lower shale member is therefore significant in adding to our understanding of the early evolution and diversity of the group. In particular, this animal is uniquely positioned, both phylogenetically and temporally, to expand our understanding of the early evolution of Hadrosaurid supracranial ornamentation.

The new species is named Aquilarhinus palimentus, where 'Aquilarhinus' means 'Eagle-nosed' and 'palimentus' means 'shovel-chin'. The specimen from which the species is described, TMM 42452-1, comprises a sphenoid fragment, both nasals, the right maxilla, the right jugal, the right quadratojugal, the partial left and right palatines, a partial right dentary, a partial first ceratobranchial, a partial neural arch of atlas, fragments of two cervical centra, two cervical ribs, a partial sacral rib, a left carpal, a nearly complete left manus, the postacetabular process of the right ilium, a fragment of right ischium, a partial astragali, pedal phalanxes III-1, and four pedal unguals. Most of the material was collected in 1983 by Thomas Lehman, Neal LaFon, and Kyle Davies, with the remainder being excavated in 1999 by Jonathan Wagoner and Thomas Lehman. The preserved parts of the skull and jaws were disarticulated but closely associated. All of these bones were found within 4 m² and clearly represent a single individual. This specimen was briefly described by Wagner in 2001 as Kritosaurus sp.  Subsequent study of the specimen, however, indicates that the new species cannot be included within Kritosaurus and differs sufficiently from other Hadrosaurids to warrant recognition a new genus and species.
 Geographical and straigraphical location of the type and referred material of Aquilarhinus palimentus. Abbreviations: cg, conglomerate; cl, clay; si, silt; ss, sandstone. Prieto-M arquez et al. (2019).
Aquilarhinus palimentus is a Hadrosaurid Dinosaur possessing nasals transversely broad across the skull table; a premaxillary shelf of maxilla at anterior apex flat and as broad as the proximal segment of the palatal process; a palatine extending nearly horizontally to contact the maxilla; and a dorsally reflected symphysial process of the dentary. It differs from all other Hadrosaurids in possessing maxilla combining jugal process and ectopterygoid ridge continuous with ventral margin of jugal facet, and differs from all other Hadrosaurids except Latirhinus uitstlani in having a nasal enclosing the extremely broad and sub-circular lateral profile of the external bony naris.

In general aspect, the skull as reconstructed was almost certainly tall and would have had a steeply sloping facial profile, as in Gryposaurus. There is circumstantial evidence to indicate that the skull roof sloped anteroventrally, and the external bony naris was exceedingly large. A remarkable departure from the generally narrow saurolophine aspect of this species is a general mediolateral expansion of the skull. This is evidenced by the broad exposure of the nasal on the skull roof, the shallow angle of inflection of the palatine vault, and the mediolateral extent of the symphysial process of the dentary. This expansion is here interpreted as dilation of the skull mediolaterally about the midline, resulting in greater separation of paired cranial elements. Dilation of the cranium appears to be a morphogenetic accommodation to the modification of the anterior dentary.

Additional Hadrosaurid elements were recovered at Rattlesnake Mountain from the same stratigraphical interval as the holotype of Aquilarhinus palimentus, some bones within a short distance of the collection site of the holotype. Although this material might pertain to Aquilarhinus palimentus, none of these isolated bones exhibit diagnostic features that would allow certain attribution. This material includes a braincase wall, a parietal bone, a frontal, a postorbital, a scapula, a humerus, a pubis, an ilium, a femur, and a tibia.

With reconstructed quadrate and skull lengths of 26 cm and 57 cm, respectively, TMM 42452-1 is a relatively small Hadrosaurid individual. For example, compared to other Hadrosaurids from the same time period, the skull of TMM 42452-1 is estimated to be only 50% the length of the skull of Gryposaurus latidens, and 65% of the length of the skulls of Acristavus gagslarsoni and Probrachylophosaurus bergei. By analogy with Gryposaurus spp. it could be assumed that the nasal arch of Aquilarhinus palimentus would become more prominent with growth. However, it is also possible that the nasal arch of Aquilarhinus palimentus experienced a different allometric growth trajectory than that of Gryposaurus spp. Therefore, Prieto-M arquez et al. are uncertain at this juncture regarding the degree of maturity of TMM 42452-1, pending the discovery of additional specimens.

Reconstruction of the skull and mandible of Aquilarhinus palimentus. Areas coloured in brown indicate bones belonging to specimen TMM 42452-1. Prieto-M arquez et al. (2019).

The presence of a gentle arch on the dorsal surface of the nasals of Aquilarhinus palimentus is reminiscent of the nasal crest in species of the Saurolophine Gryposaurus. Gryposaurus ranges from the early Campanian to possibly the late Maastrichtian and is distributed from southern Canada to south-western Texas Notably, Gryposaurus latidens, from lower Campanian strata of the Two Medicine Formation of Montana, represents one of the oldest known Hadrosaurids, with an estimated age of 80 million years. A nasal arch is also present in Rhinorex condrupus, a sister taxon to Gryposaurus spp. from the Neslen Formation of eastern Utah, in late Campanian strata dated to 75–74.5 million years ago. Despite sharing an arcuate dorsal profile of the nasal, Aquilarhinus palimentus is clearly different from Rhinorex condrupus and Gryposaurus spp. The external bony naris (at least the dorsal extent) of Gryposaurus spp. and Rhinorex condrupus is significantly narrower anteroposteriorly than that of Aquilarhinus palimentus. The maxilla of Gryposaurus shows a jugal tubercle instead of a jugal process, and its premaxillary shelf is steeply inclined at least 40° relative to the tooth row compared to the less inclined shelf of quilarhinus palimentus which is inclined at 30 °. Finally, the anterior process of the jugal of Gryposaurus and Rhinorex condrupus is substantially deeper with a relatively short anterior apex, compared to the shallow process and long apex of Aquilarhinus palimentus.

Right nasal of the holotype specimen (TMM 42452-1) of Aquilarhinus palimentus. (A) Lateral view; (B) interpretive line drawing of the lateral view; (C), medial view; (D), interpretive line drawing of the medial view. Dark grey indicates reconstruction, cross hatching indicates broken surfaces, open circles represent concretionary matrix. Prieto-M arquez et al. (2019).

Naashoibitosaurus ostromi is a Kritosaurin Saurolophine originally described on the basis of a skull and fragmentary postcranium. The nasals display a low but acute arch. Unlike Aquilarhinus palimentus, however, the nasal crest of Naashoibitosaurus ostromi lies farther posterodorsally relative to the posterior margin of the external bony naris. Most notably, the posterodorsal margin of the external bony naris is very narrow in Naashoibitosaurus ostromi, less than half the width of the broad sub-circular margin enclosed by the nasal of Aquilarhinus palimentus. In addition, a deep circumnarial fossa excavates the lateral surface of the nasal surrounding the external bony naris of Naashoibitosaurus ostromi, whereas the fossa is distinctly shallower in Aquilarhinus palimentus. As in other Hadrosaurids, but unlike Aquilarhinus palimentus, the maxilla of Naashoibitosaurus ostromi shows a dorsal jugal tubercle rather than a jugal process and the occlusal plane displays a maximum of two functional teeth. The dorsal surface of the premaxillary shelf is concave and substantially narrower, about half the width of that in Aquilarhinus palimentus. Similarly, the palatal process of Naashoibitosaurus ostromi is much shallower, about half the depth seen in Aquilarhinus palimentus.

Although the premaxillae of Aquilarhinus palimentus were not recovered, there is no indication that the bizarre mandibular symphysial configuration in this species was related to the circumnarial structure, nor is it likely to be related to any part of the vocal, thermoregulatory, defensive or other physiological behavioural systems functionally linked to the rostrum. Prieto-M arquez et al. consider it more likely that the autapomorphic dentary symphysis is linked to restructuring of the rostrum for a unique feeding strategy. The projection and curvature of the symphysial processes of the dentary, nearly horizontal palatines and wide nasals all suggest that this animal was broad snouted, if not simply broad headed, also suggesting trophic adaptation. The dentaries and their symphysial processes would have met in a ‘W’-shaped section anteriorly. Assuming the predentary retained its ancestral relationships to the features of the anterior dentary, it would have been shaped like two trowels laid side to side. The raised symphysis might have led to a raised ridge that passed between the concave predentary fossae along the midline, much like the strengthening ridge leading from the handle onto the blade of a spade or shovel. The anterior extension of the symphysial processes, and the general proportions of the dentaries, suggests that the predentary may have been relatively long.

The hypothesized shovel-shaped ‘bill’ and widening of the skull in Aquilarhinus palimentus may have been adapted for shovelling out and scooping up vegetation. The central reinforcing ridge developed from the dentary symphysis would produce two strong arches in cross section to resist the strain of pushing through sediment or vegetation. The dentary was straightened relative to that of ancestral Hadrosaurids, likely in order to bring the predentary into alignment with the axis of the mandibles, reducing bending stress along the length of the bone and keeping material from falling out of the predentary. The widening of the mandible, and corresponding widening of the cranium, produced a wider ‘scoop’.

The adaptations of this animal, as interpreted by Prieto-M arquez et al., bring to mind those of Gomphotherid Proboscideans, Sirenians, Hippopotamus, the South American Pyrotheres and, especially, Desmostylians. These groups are or were relatively large-bodied herbivorous Mammals, many either semiaquatic or closely related to aquatic forms. Moreover, these taxa share narial specializations, as also occur in Hadrosaurids. These analogies suggest that Aquilarhinus palimentus may have been a paralic, possibly semiaquatic species specialised for digging in loose wet sediment. This habitus is consistent with the facies interpretation of the strata in which the type specimen was found.

Trophic specialization does not seem exceptionally common among Hadrosaurids; some non-Hadrosaurids (e.g. Protohadros byrdi) and the Lambeosaurine Angulomastacator daviesi have strongly ventrally deflected rostra, but a direct connection to feeding habits has not been proposed. Some palaeontologists have have proposed trophic specializations based on the diameter of the premaxillary ‘beak’. While this is understandable, Prieto-M arquez et al. feel that until the morphogenetic relationship between the beak and the circumnarial fossa can be explored in detail, it is wisest to consider this tentative. The conformation of the dentary symphysis in Aquilarhinus palimentus is so far the most likely candidate for a clear trophic specialisation among Hadrosaurids.

Ancestral state reconstructions for the presence of an osseous cranial crest (in its simplest form, an elevation of the skull roof above the sub-horizontal ancestral cranial profile) indicate that the most recent common ancestor of the clade including Saurolophidae and the Aquilarhinus-Latirhinus lineage probably sported a crest. The presence of a cranial crest was also likely ancestral for Saurolophids as a whole, including both Lambeosaurines and Saurolophines. Therefore, the ‘solid crests’ of Saurolophines and the ‘hollow crests’ of Lambeosaurines are most likely homologous. It would, then, be less appropriate to say that the crest has evolved several times among Saurolophids, and more reasonable to suggest that it is the conformation of the crest, not the presence or absence of a crest, which has been most labile among Hadrosaurids.

Both parsimony and maximum likelihood optimization methods support the hypothesis that the arched nasals of Aquilarhinus palimentus did not evolve independently from those of derived Hadrosaurids such as Gryposaurus and other Kritosaurins that are deeply nested within Saurolophinae but are in fact homologous. This may indicate that the arched nasal crest is the ancestral conformation of the crest, and all other Hadrosaurid crests are ultimately derived from the arched nasal crest.

The lack of sufficient cranial material in Hadrosaurus foulkii prevents ascertaining whether crests were ancestral for Hadrosauridae. The unadorned skull of another non-Saurolophid Hadrosaurid, Eotrachodon orientalis suggests tentatively that the earliest Hadrosaurids lacked supracranial crests. On the other hand, osseous crests must have been lost at least twice within Saurolophinae (Acristavus gagslarsoni and Edmontosaurini) and might have been lost in Eotrachodon orientalis as well. So far, there is only evidence that enclosure of the nasal passages to form a ‘hollow’ crest occurred once, in Lambeosaurines. However, this must have happened quite early in their evolution.

Aquilarhinus palimentus represents a new genus and species of Hadrosaurid from the early Campanian of south-western Texas. This taxon is characterised by several autapomorphies of the facial skeleton, the most remarkable of which consists of a dentary symphysis that is reflected dorsally as well as anteromedially projected. The latter condition, along with evidence of a relatively broad skull, suggest that this Hadrosaurid may have fed by shovelling material, possibly soft water plants.

This new species is one of the oldest Hadrosaurids and one of the few non-Saurolophid Hadrosaurids known to date, forming a group of ‘broad-nosed’ forms with Latirhinus uitstlani that branched off before the major clades Saurolophinae (‘solid-crested’ and unadorned taxa) and Lambeosaurinae (‘hollow-crested’ taxa). This adds to the diversity of pre-Saurolophid taxa known to date, previously restricted to Hadrosaurus foulkii and Eotrachodon orientalis, and suggests the existence of a previously unrealized diversity of Hadrosaurid lineages that evolved prior to the main radiation of the clade.

Supracranial crests were possibly present ancestrally in non-Saurolophid Hadrosaurids, as well as in the common ancestor of Saurolophidae, Saurolophinae and Lambeosaurinae. Prieto-M arquez et al. find evidence in support of nasal arches as the ancestral crest morphology, from which other derived types of supracranial ornaments evolved within Saurolophid Hadrosaurids.

See also...
Follow Sciency Thoughts on Facebook.

Sunday, 10 November 2019

Investigating the origins of sedentism and plant cultivation in northeast China.

The transition to a sedentary way of life and the domestication of plants is arguably the most significant ‘revolution’ in human history. This transition gradually resulted in a dramatic increase of population size and density, in craft specialisation and the division of labour and the initiation of social dynamics and the accumulation of resources that are linked to the development of socio-political stratification. The processes, mechanisms and possible drivers of a transition from one subsistence mode to another have long been at the forefront of anthropological and archaeological research. Three hypotheses have been proposed to explain such transitions. The first suggests that stress, induced either by deteriorating environmental conditions (the ‘oasis hypothesis’) or by population increase led to an overexploitation of the environment and forced innovation. A current example is the optimal foraging theory and the diet breadth model, which predict that a transition to a delayed returns system (i.e. long-term tending resources) will occur during times of scarce resources, promoting a border dietary range. The second hypothesis argues that transitions occur at times of enhanced resources. A current example is the cultural niche construction theory, which claims that organisms shape their environment during stable or affluent times, these allow experimentation with locally available resources, which improve crop yield and eventually lead to domestication. The third hypothesis argues that transitions occur as a result of socioeconomic competition and are not affected by external forcings.

In a paper published in the journal PLoS One on 18 July 2019, Gideon Shelach-Lavi of the Department of Asian Studies at The Hebrew University of Jerusalem, and the Center for Frontier Archaeology at Jilin University, Mingyu Teng, also of the Center for Frontier Archaeology at Jilin University, Yonaton Goldsmith of the Department of Geological and Planetary Sciences at the California Institute of Technology, and the Institute of Earth Sciences at The Hebrew University of Jerusalem, Ido Wachtel of the Department of Archaeology at The Hebrew University of Jerusalem, Chris Stevens of the Institute of Archaeology at University College London, Ofer Marder of the Department of Bible Studies at Ben-Gurion University, Xiongfei Wan of the Institute of Archaeology and Cultural Relics, Xiaohong Wu of the School of Archaeology and Museology at Peking University, Dongdong Tu, again of the Department of Asian Studies ar The Hebrew University of Jerusalem, Roi Shavit, also of the Department of Bible Studies at Ben-Gurion University, Pratigya Polissar of the Lamont Doherty Earth Observatory, Hai Xu of the Institute of Surface-Earth System Science at Tianjin University, and Dorian Fuller, also of the Institute of Archaeology at University College London, present evidence for the timing, duration and environmental conditions of the onset of sedentism and plant cultivation in northern China, the second oldest center of domestication in the Old World.

Shelach-Levi et al. address the first two hypotheses by examining whether the onset of sedentism and cultivation occurred at a time of stress or affluent conditions and whether these environmental conditions were stable or fluctuating. They assume that the limiting environmental parameter is rainfall and thus we focus on the timing of rainfall changes and human settlement patterns at the onset of sedentism and cultivation in north China. They acknowledge the possibility that temperature might have also played a role in restricting Millet growth, however, as the magnitude, timing and seasonal structure of temperature change in north China in uncertain, they focus on rainfall. The combination of high-resolution archaeological and palaeoclimatic data enable to test the theoretical frameworks of the onset of sedentism, domestication and population increase.

North China is one of a few centres in the world where complex agricultural systems emerged independently. The native staple grains are two types of Millet (Foxtail and Broomcorn), however, the date, process and the palaeoclimatic context of their domestication are debated. Shelach-Levi et al. focus on northeast China because currently the earliest undisputed examples of domesticated Millet grains and the most extensive evidence for early Millet consumption have been found in this region, at sites of the Xinglongwa culture.

Early research in north China began in the 1970s and focused on the middle reaches of the Yellow River. It identified remains of early Neolithic sedentary societies of the 7th and 6th millennia BC, which were sorted into a series of ‘cultures’, most notably Cishan and Peiligang. These findings focused attention to this area – which classical Chinese tradition identifies as ‘the cradle of Chinese civilization’, the birthplace of agriculture from whence it spread to other regions in north and central China. By the late 1980s, it became clear that contemporaneous sedentary societies also existed in other regions of north China, including the Houli culture in the lower Yellow River area and the Xinglongwa culture in Northeast China. In recent years even earlier phases of the 'Neolithic' period were identified in the different sub-regions of North China, such as the Xiaohexi phase in the northeast, but those are not well studied and are poorly dated. While substantial archaeological knowledge of sedentary prehistoric societies has been presented, the earlier phases that preceded the sedentary cultures and the transition process from mobile to sedentary societies remains mostly obscure. To address these developments and their context during the important phase of the transition to agriculture, Shelach-Levi et al. integrate novel data from the excavations of two early Neolithic sites, the results of two high-resolution archaeological surveys in northeast China and novel palaeoclimatic data.

Over the past 20 years, four high-resolution, detailed, large-scale regional archaeological surveys have been conducted in northeast China. Shelach-Levi et al. focus on the surveys conducted around the modern cities of Chifeng, in Inner Mongolia, and Fuxin, in Liaoning Province, because these are the only surveys that recovered evidence of the earlier phases of sedentism. These surveys were designed to systematically recover data that enable population estimates and the reconstruction of local socio-political trajectories. The full area was systematically surveyed on foot (at a 50 and 20 m resolution), the locations and densities of pottery shards and stone tools were mapped, counted and statistically analyzed. A total pottery amount was calculated for each period by integrating the area of the occupied territory, the density of artifacts and the length of each period. These results provide a direct reconstruction of population trajectory in these two regions and present a qualitative demographic history of northeast China. The earliest sites found in both regions are those attributed to the Xiaohexi phase and the Xinglongwa culture, which represents the earliest phase of sedentism in this region. The combined results of the two surveys demonstrate a rapid increase in population and the complexity of village society following the initial stage of sedentism.

Map of the survey areas and the palaeoclimate records discussed. Shelach-Levi et al. (2019).

To evaluate the timing and socio-economic processes involved in the transition to sedentism, Shelach-Levi et al. excavated two single-occupation sites discovered during our survey in the Fuxin area. Those sites capture the onset and earliest phases of sedentism.

At the earlier site, 12D56 (also named Jiajiagou west site 贾家沟西遗址), the excavation exposed a single-occupation, irregular-oval structure of ~3.5 m in diameter, which contained ash, pottery and stone tools. Based on seven ¹⁴C ages, the site was occupied between 7900 and 7750 years ago (5900-5750 BC). This is the first time that a Xiaohexi phase site is radiocarbon dated. Previous research, based on ceramic typology, suggest dates in the 7th and even 8th millennium BC, but according to Shelach-Levi et al.'s findings the date of this phase cannot be earlier than 6,000 BC. The shape of the structure we excavated is also different from the supposedly rectangular structures reported for some Xiaohexi sites. At some of those sites the rectangular structures may belong to a later Xinglongwa occupation and in others the report is not detailed enough to examine the shape of the structures. Thus, it is possible that in other sites as well, structures were oval or that both oval and rectangular shape structure existed during this period.

The 12D56 site. Plans of the excavation site showing the structures excavated (solid lines are places where the perimeter of the structure was excavated, dashed lines represent extrapolation of the structure parameter and are provided as context reference, shading is pottery density (shard/m²). Shelach-Levi et al. (2019).

About three hundred potshards were excavated from this site. There are are crude, soft and crumbly, similar in style and quality to those known from other Xiaohexi sites. Most shards are unadorned, but a few pots are decorated with appliqué and narrow bands of diagonal incisions. 330 stone artifacts were also recovered, including ground and chipped stone tools. Of the ground stone tools, almost 80% are spades. Although no use-wear analysis was done, the fact that those artifacts, which are not known from earlier periods in the region, are so dominate suggest that they are associated with new set of activities, probably related to the clearance of woods and the cultivation of the land Similar artifacts are known form other site dated to the Xiaohexi phase.

Artifacts excavated at site 12D56. Stone artifacts (upper half) and pot shards (lower half). Shelach-Levi et al. (2019).

Floral remains from the site consist of a predominance of wild fruits and nuts and a small amount of wild Panicum Millet (Panicum miliaceum ruderale). The two seeds that were recovered are small in size and are representative of what is expected of grains from early cultivated plants in the initial process of domestication.

At the later site, 12D16 (also named Tachiyingzi site 塔尺营子遗址), Shelach-Levi et al. excavated an area of ~40 m² out of a much larger site. Based on ten ¹⁴C ages, the site was occupied between 7.5–7.4  thousand years ago (5500-5400 BC). The area excavated contained a rectangular structure measuring about 7.5 × 6.5 m and remains of at least one additional structure. The shape of the structure is identical to those known from the nearby site of Chahi (查海), where a large area of the site was exposed revealing a densely occupied Xinglongwa period village.

The 12D16 site. Plans of the excavation site showing the structures excavated (solid lines are places where the perimeter of the structure was excavated, dashed lines represent extrapolation of the structure parameter and are provided as context reference, shading is pottery density (shard/m²). Shelach-Levi et al. (2019).

The structure in this area was severely burned during or after its abandonment and remains found on its floor indicate that it was supported and covered with large oak beams. On its floor Shelach-Levi et al. recovered 22 complete ceramic vessels of typical Xinglongwa culture. The quality of ceramic production is high and most are highly decorated with incised motifs. The stone artifacts are more abundant and diverse than those of site 12D56 (1003 such artifacts were found at site 12D16), and show evidence for highly standardised pressure bladelets produced on-site, as a household routine. The ground stone assemblage consists of grinding stones, polished axes and adzes, spades, pounders and hammer-stones.

Artifacts excavated at site 12D16. Stone artifacts (upper half) and ceramic vessels (lower half). Shelach-Levi et al. (2019).

Floral remains include a few millet seeds but are predominantly composed of wild fruits and nuts. Sixteen millet grains are identified as Common Millet (Panicum miliaceum). Their size is small, on average 1.25–1.70 mm in length and 1.05–1.40 mm in width, closer to the wild type Panicum (Panicum miliaceum ruderale) than to modern domesticated Broomcorn. These grains seem to represent plants that are not yet fully domesticated, but represent an early phase in a sequence of size change expected to take 2–3 thousand years.

Remains of Common Millet (Panicum miliaceum) from site 12D16. Shelach-Levi et al. (2019).

To evaluate northeast China’s palaeo-hydroclimate during the transition to domestication and sedentism, Shelach-Levi et al. integrated data from Dali lake-level to provide an estimate of rainfall change, and Lianhua Cave oxygen isotopes to provide continuous, high-resolution absolute dating. In addition, they analysed the isotopic contents of soil alkanes from both archaeological sites, which primarily records the isotopic composition of rainfall. Alkanes are organic compounds produced in leaf waxes incorporating oxygen and hydrogen derived from water. These can be preserved in in soils and give a record of the ratios of different isotopes of the elements within the local water when the plant was growing. When air masses hit areas of high ground and are uplifted, they cool and preferentially precipitate moisture with the heavier isotopes of oxygen and hydrogen, thus the ratio of these isotopes in the preserved alkanes in the soil gives a measure of how high up and how far from the source water the soil was when it formed. The palaeoclimate records show similar hydroclimate patterns. Between 9000 and 8100 years ago (7000-6100 BC) relatively dry conditions prevailed in northeast China. Between 8100 and 7900 years ago (6100-5900 BC) a sharp substantial increase in rainfall amount occurred. The Lianhua Cave record shows a 2.5‰ (2.5 parts per thousand) isotope change at 8100 years ago (6100 BC), which is only comparable in magnitude to the transition from the Younger Dryas to the Early Holocene at 11 500 years ago (9500 BC). The soil alkanes are more depleted in heavy isotopes at the later 12D16 site than the the earlier 12D56 site and is thus in agreement with the other records. The relatively wet conditions prevailed for  about 400 years. A decrease in rainfall amount occurred between 7550 and 7400 years ago (5550-5400 BC). This transition appears in both records, though the timing of the rainfall decline differs by about 150 years.

The onset of sedentism, cultivation and the early phase of domestication in northeast China is an important test case for studying the theoretical frameworks for the transition to agriculture. The transition to sedentism in the Xiaohexi phase is defined by investment in permanent structures, unknown in this region in prior periods, the dramatic increase in the production of pottery found at all sites in relatively large quantities, and the presence of large grinding stones. The empirical coincidence of the onset of sedentism and cultivation about 7900 years ago (5900 BC) with the transition to a significantly wetter climate between 8100 and 7900 years ago (6100-5900 BC) suggests that affluent conditions played an important role in facilitating the onset of these processes in northeast China. Shelach-Levi et al.'s results suggest that in northeast China, fundamental and multi-scale changes occurred not due to necessity or stress but rather under stress-free affluent conditions and thus support the affluency hypothesis. Such plentiful resources allowed Human communities to settle down in one place and enhance their interaction with their immediate environment, without the need to migrate in search of food.

The Xinglongwa culture thrived throughout this affluent period and declined within a century from the end of the wetter condition. This strengthens the notion that affluent climatic conditions were an important factor in the ability of this culture to thrive.

Sedentism and plant cultivation initiated simultaneously, but sedentism and the development of a complex village society matured much faster. The initial phase of sedentism, in the Xiaohexi phase is typified by small sites with makeshift irregular-shaped huts, which suggest low investment in construction and perhaps short life-use. This phase rapidly transitioned into the full-fledged Xinglongwa culture in which large scale-villages containing up to 40 domestic structures, represent an increase in community size that coincided with a rapid increase of regional population levels. Rectangular domestic structures, like the one excavated at site 12D16, and community-wide projects, such as the ditch that surrounded the Chahai site, suggest substantial investment, and communal construction efforts.

Simultaneous processes, such as the intensification of craft production and improvement of ceramic and stone tool technologies, suggest a development of craft specialisation and economic intensification. Similar developments are known from other parts of north China, suggesting that the processes described by Shelach-Levi et al. were shared by many contemporaneous societies.

The process of plant domestication progressed at a much slower pace. Elsewhere, researchers argue for an earlier date of Millet domestication and use in other regions of North China. However, because they use different types of data it is difficult to compare their results to those of Shelach-Levi et al. According to their study, evidence for its initiation (i.e. collection of plants that later will be domesticated and probably the cultivation of wild plants) is found at site 12D56, even after 500 years it was not yet completed at site 12D16. Moreover, the percentage of domesticated foods seems to have remained limited even during the height of the Xinglongwa period. Shelach-Levi et al.'s results disagree with earlier studies that found Human bone carbon isotopes from the Xinglongwa period suggestive of a grain (possibly Millet) dominated diet. Future research will be needed to resolve these contradictions. Recent evidence from other parts of North China suggest that like the process Shelach-Levi et al. describe for the Fuxin area, there too the trajectory of domestication and transition to agriculture was relatively long. In the initial phases, addressed by Shelach-Levi et al., it was not domestication per-se which was important but the cultivation of the land (indicated by the large number of spades found at site 12D56) and the harvesting and consumption of durable food resources such as seeds (of domesticated and wild plants), nuts (such as Acorn and Walnut) and wild fruits (Apricot, Amur Cork). Those resources were collected in large quantities, stored for long periods, and thus enable a year-long occupation of the same site and the stable support of larger communities. Based on the data they collected, Shelach-Levi et al. suggest that the suite of traits that found in the earliest phase sedentism, expansion into new types of food resources and perhaps cultivation, were the driving force behind domestication and not vice-versa.

The archaeological, botanical and palaeoclimatic data presented above help clarify the context of the transition to a sedentary way of life, plant cultivation and initial stages of plant domestication in Northeast China. The multi-dimensional nature of Shelach-Levi et al.'s data allow them to suggest that these processes occurred during a period of comparative affluence that enabled population increase and experimentation with new resources and technologies. Our botanical findings support the view that the domestication process took a long time after Humans started cultivating plants, as has been demonstrated for several other crops in other regions, and that not all the plants that were initially cultivated or intensively collected were botanically transformed and became domesticated. These observations, which may not be true for all cases of independent transitions to sedentary agricultural societies, are crucial for a global view of the evolution of Human society. They suggest that at least in some cases, fundamental and multi-scale changes occurred not due to necessity or under stress but rather because of opportunities to experiment and expand under stress-free affluent conditions.

See also...
Follow Sciency Thoughts on Facebook.