Jiucaiyuangnathus confusus: A new species of Baurioid Therocephalian from the Eartly Triassic of Xinjiang Province, China.

The Bogda Mountains of northeastern Xinjiang Province, China, preserve a Permian-Triassic sequence which has produced a broad range of terrestrial Vertebrates, including non-Mammalian Therapsids such as Dicynodonts, Gorgonopsians, and Therocephalians. Two Therocephalians have been described from this sequence to date, Urumchia lii from the Early Triassic Jiucaiyuan Formation, and Dalongkoua fuae from the Late Permian Guodikeng Formation, although several other species are known from elsewhere in North China, including Shiguignathus wangi, Jiufengia jiai, Euchambersia liuyudongi, and Caodeyao liuyufengi from the Late Permian Naobaogou Formation of Inner Mongolia, Moschowhaitsia lidaqingi from the Late Permian Wufoshi Formation of Gansu Province, Hazhenia concava from the Early Triassic Heshanggou Formation of Inner Mongolia, Ordosiodon lincheyuensis, Ordosiodon youngi and Nothogomphodon sanjiaoensis from the Early Triassic Ermaying Formation of Shanxi Province, Yikezhaogia megafenestrala. from the Early Triassic Ermaying Formation of Inner Mongolia, and Traversodontoides wangwuensis from the Middle Tirassic Ermaying Formation of Henan Province.

In a paper published in the journal Vertebrata PalAsiatica on 20 July 2024, Lui Jun of the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences and the College of Earth and Planetary Sciences of the University of the Chinese Academy of Sciences, and Fernando Abdala of the Área de Paleontología at Unidad Ejecutora Lillo and the Evolutionary Studies Institute at the University of the Witwatersrand, describe a new species of Baurioid Therocephalian from the Early Triassic Jiucaiyuan Formation of Jimsar County in Xinjiang Province, China.

The new species is described from a slab on which a partial snout and several postcranial skeletal elements were visible on the surface. When X-ray microcomputed tomography was applied to this slab it was discovered that two largely disarticulated partial skeletons were present within. The partial skeleton is designated as the holotype of the new species (in taxonomy, a specimen is named as the holotype when an new species is discovered, and any other specimens are deemed to belong to that specie species if the can be shown to belong to the same species as the holotype), which is given the name Jiucaiyuangnathus confusus, where 'Jiucaiyuangnathus' means 'Jiucaiyuan-jaw', in reference to the Jiucaiyuan Formation, and 'confusus' means 'confusing' in reference to the difficulty had deciphering the specimens. It is thought that the snout is derived from one of the post-cranial skeletons, but it is impossible to tell which.

Jiucaiyuangnathus confusus (IVPP V32945, holotype) from Jimsar, Xinjiang. (A)–(C) photo (A) and 3D rendering (B) of the left side of the snout in lateral and 3D rendering of the medial view of the left side of the snout (C); (D). 3D rendering of the snout in posterior view showing the bones as preserved. Abbreviations: afo. anteriormost foramen; cc. christa choanalis; F. frontal; L. lacrimal; l.c. lacrimal canal; M. maxilla; m. maxillary tooth; m.a. maxillary antrum; msf. maxillo-septomaxillary foramen; pdl. dorsal layer of palatine; pit. maxillary round pit; PL. palatine; PM. premaxilla; pml. medial layer of palatine; sH, sinus Highmore; SM. septomaxilla; V. vomer. Lui & Abdala (2024).

The preserved portion of the jaws has five surviving incisors and lacks canines. There is a diastema (gap) between the last incisor in the upper jaw and the first maxillary tooth, but no equivalent gap is present in the dentition of the lower jaw, traits consistent with Jiucaiyuangnathus confusus being a Baurioid Therocephalian.

3D rendering of Jiucaiyuangnathus confusus (IVPP V32945, holotype) from Jimsar, Xinjiang . (A) The preserved snout in ventral view; (B), (C) vomer in dorsal (B) and ventral (C) views, vomer is reconstructed in the natural position in (C); (D) left dentary in lateral view; (E), (F) mandibles in dorsal (E) and ventral (F) views. Abbreviations: 1st ic. first incisor; ch. choana; D. dentary; d. dentary tooth; F. frontal; for vn. place for vomeronasal organ; M. maxilla; N. nasal; PL. palatine; PM. premaxilla; SP. splenial; V. vomer; v.f. vomerine foramen. Lui & Abdala (2024).

The two partial skeletons are given the designations IVPP V32946-1 (which is marginally the smaller of the two) and IVPP V32946-2 (which is marginally the larger). While both are largely disarticulated, most of the bones are close to their original positions, making it possible to assign them to one of the two skeletons wirh confidence. In both skeletons, the neural arches are separate from the centra of the vertebrae, making it likely that they were juveniles at the time of death.

Posterior skeletons of Jiucaiyuangnathus confusus (IVPP V32946) from Jimsar, Xinjiang  (A), (B) photo of the slab; (C), (D) 3D rendering of bones. Gray (IVPP V32946-1) and light purple (IVPP V32946-2) are bones of each specimen. Light blue uncertain. Lui & Abdala (2024).

Specimen IVPP V32946-1 has ten presacral vertebrae preserved, the the atlas and axis, five thoracics, and three lumbars, as well as three sacral vertebrae and a series of at least 11 caudal vertebrae, five of them being rod-like. There are three short, curved cervical vertebrae, and five incomplete ribs on the left side and seven nearly complete ribs on the right side of the thoracic vertebrae. An almost complete pelvic girdle lacks only the left ischium. A right femur, lacking a proximal end and with an incomplete distal end, probably belongs to this skeleton.

3D rendering of Jiucaiyuangnathus confusus  (IVPP V32946-1) from Jimsar, Xinjiang.  (A), (B) The preserved skeleton in dorsal (A) and ventral (B) views; (C) right femur in distal view; (D)–(F) atlas and axis in anterior (D), left (E), and right (F) lateral views; (G) four thoracic vertebrae in right lateral view; (H), (I) sacral region in lateral (H) and dorsal (I) views; (J) caudal vertebrae Abbreviations: aic. atlas intercentrum; cdr. caudal rib; cdv. caudal vertebra; cr. cervical rib; FE. femur; lv. lumbar vertebra; ns. neural spine; sr. sacral rib; sv. sacral vertebra; tp. transverse process; tr. thoracic rib; tv. thoracic vertebra. Lui & Abdala (2024).

Specimen IVPP V32946-2 has ten continuous vertebrae, interpreted as thoracics, as well as 13 complete long left thoracic ribs and the proximal side of eight right thoracic ribs. The head of the first sacral rib is considerably expanded dorsoventrally with a short, stout shaft curving ventrally and a very expanded distal end to contact the ilium. This specimen has a nearly complete left scapula and the dorsal portion of the right scapula, as well as a separated procoracoid, which lies close to the ventral side of the scapula. An incomplete interclavicle appears as a broad flat bone that gently curves ventrally, and the sternum is preserved as a large, thin, longer than wide flat plate. Again, the pelvic girdle is almost complete, in this case lacking the left pubis. The proximal parts of both femurs are preserved, with the right being more complete.

3D rendering of Jiucaiyuangnathus confusus (IVPP V32946-2) from Jimsar, Xinjiang. (A), (B) Skeleton in dorsal (A) and ventral (B) views; (C) part of thoracic vertebrae in left lateral view; (D) two sacral and three anterior caudal ribs; (E)–(H) sacral ribs of (D) in dorsal (E), (G) and ventral (F), (H) views; (I)–(L) two smaller sacral ribs in dorsal (I), (K) and ventral (J), (L) views Abbreviations: cdr. caudal rib; mt. metatarsal; sr. sacral rib. Liu & Abdala (2024).

Neither of the skeletons has neural arches fused to the centra, suggesting that they were both juveniles when they died, but the neural arches of the smaller skeleton are more distant from the centra than in the larger, possibly suggesting that it was younger and less developed. There are also differing degrees of ossification in the bones of the pelvic girdle of the two skeletons, which again suggest different levels of development. 

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Understanding the orientation of graves in the Bronze Age Gumugou Cemetery of Xinjiang Province, China.

Many cultures bury their dead with a preferred orientation, and understanding how this is chosen can tell us a great deal about the beliefs of a culture. The orientation of graves has been extensively studied for ancient European and Mediterranean cultures, demonstrating that burials were often aligned with both terrestrial and celestial objects of importance by ancient peoples, but has been less well studied in other parts of the world.

In a paper published in the Journal of Archaeological Science: Reports on 17 February 2024, Jingjing Li of the Xinjiang Astronomical Observatory, Jarken Esimbek, also of the Xinjiang Astronomical Observatory, and of the University of the Chinese Academy of Sciences, and Yingxiu Ma, again of the Xinjiang Astronomical Observatory, examine the orientation of graves in the Bronze Age Gumugou Cemetery of Xinjiang Province, China.

The Gumugou Cemetery is located on the eastern fringe of the Taklimakan Desert, in the Tarim Basin, to the north of the now dry Kongque (Peacock) River and about 70 km to the west of the Lop Nor Salt Lake. The cemetery has been dated to between 3800 and 3400 years before the present, and along with a series of related sites within the region between Lop Nor and the Taklimakan Desert, is considered representative of one of the oldest known Bronze Age cultures within Xinjiang Province.

Location of the Gumugou Cemetery and other archaeology sites in the Tarim Basin, Xinjiang. Li et al. (2024).

The Gumugou Cemetery site was excavated in the winter of 1979 by an expedition from the Xinjiang Institute of Archaeology under the leadership of Binghua Wang. A total of 42 burials were discovered and excavated, all within an area of 1600 m³. The burials could be divided into two types, with six Type I burials forming an upper layer, and 36 Type II burials forming a lower layer. 

The Type I burials are quite often placed above Type II burials, and are surrounded by seven rounds of timber posts. These Type I burials apparently contained wooded coffins, which have long decayed away, leaving the (well preserved) Human remains exposed. A small amount of grave goods were present. 

Surface of Type I burials of the Gumugou site. Li et al. (2024).

Type II burials form a lower layer and each contain a single body placed within a boat-shaped coffin between two posts, one at the head of the coffin and one at the feet. These contained more numerous grave goods, including pointed felt hats, leather, woollen capes, grass woven baskets, bone and stone artifacts, wheat grains, and Ephedra twigs. While grave goods were more numerous in the Type II burials than the Type I burials, there was otherwise little to differentiate them, and they are presumed to have come from the same culture.

Part of Type II burials of Gumugou Cemetery. Binghua Wang in Li et al. (2024).

The tombs are aligned roughly along an east-west axis, with their heads to the east, which, combined with the posts surrounding the Type I burials, which resemble solar rays, was taken as evidence of sun-worship by the people who used the cemetery.

However, Wang took care to record every detail about the graves, including the azimuth of each burial (the azimuth is an orientation relative to true north, where north is 0°, east is 90°, south is 180°, etc.). Li et al. collated this data, and compared it to a calculated solar arc for sunrises at the site. A solar arc of sunrises is made up of the azimuth of the sunrise throughout the year, giving an arc (in the Northern Hemisphere) with the Summer Solstice to the north and the Winter Solstice to the south. At the Gumugou Cemetery the sunrise azimuth is 57.7° on the summer solstice and 120.8° on the winter solstice, while the graves have azimuths of between 102° and 58°.

Orientations of the grave in Gumugou cemetery. Li et al. (2024).

The region where the Gumugou Cemetery is located has an arid desert climate with temperatures reaching as high as 40°C in the summer and falling as low as -20°C in the winter, and strong winds in spring and autumn leading to dust storms which can cause potentially lethal respiratory illnesses. The graves in the cemetery contain men and women, adults and children, with no apparent connection between age and/or gender of the occupant and the type of burial, the amount of grave goods, or the orientation of the grave. 

The graves vary in orientation, but are clustered around azimuth directions of 90° and slightly north of this. If the graves were orientated in line with the orientation of the sun at the time of burial, as Li et al. suspect, then the overwhelming majority of the dead would have been buried at or around the Spring and/or Autumn Equinoxes. Since it is unlikely that people were only dying at these times of year, Li et al. instead suggest that the graves represent secondary burials, with the dead being stored elsewhere until the favoured season of funerals.

Histogram of aligned skeletons. Li et al. (2024).

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Magnitude 7.1 Earthquake on the border between China and Kyrgyzstan.

The China Earthquake Networks Center recorded a Magnitude 7.2 Earthquake at a depth of 22 km beneath Wushi County in western Xinjiang Province, China, close to the border with Kyrgyzstan slightly before 2.10 am local time on Tuesday 23 January 2024 (slightly before 6.10 pm on Monday 22 January, GMT). The are no reports of any damage or injuries associated with this event at the time of writing, although people have reported feeling it across much of eastern Kyrgystan.

The approximate location of the 23 January 2024 Xinjiang/Kyrgyzstan border region Earthquake. USGS.

The Tian Shan Mountains stretch for 2500 km across Xinjiang, Kazakhstan, Kyrgyzstan and Uzbekistan. The Tian Shan are part of the Himalayan Orogenic Belt, mountains in Central Asia pushed upwards by the collision of India and Asia. The Indian Plate is currently pushing into the Eurasian Plate from the south at a rate of 3 cm per year. Since both are continental plates, which do not subduct, the Eurasian Plate is folding and buckling, causing uplift in the Himalayas and other mountains of Central Asia. This is not a smooth process, the rocks will remain effectively stationary for log periods of time while pressure builds up, then give suddenly, releasing large amounts of energy in the form of Earthquakes.

The movement of India relative to Asia, and the blocks within the eastern part if the Eurasian Plate. University of Wollongong.

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Eresus da & Eresus yukuni: Two new species of Velvet Spider from Xinjiang Province, China.

Velvet Spiders, Eresidae, are a group of highly distinctive Spiders with an almost exclusively Old World distribution (a single species is known from Brazil). They are often brightly coloured (some species are known as Ladybird Spiders for this reason) and typically live within underground tubes lined with silk, acting as ambush predators in areas with low vegetation, and well drained soil. Unusually for Spiders, some species are social, living in large colonies which co-operate in the raising of young. Parental care is a one of the distinguishing features of Velvet Spiders, with the females actively feeding their young for some time after hatching, liquefying their own internal organs in order to do so. The bright colours and distinctive behaviour of Velvet Spiders, combined with a preference for land also favoured by Human farmers, has led to many species having protected status.

In a paper published in the Biodiversity Data Journal on 6 December 2022, Yejie Lin of the Hebei Key Laboratory of Animal Diversity at Langfang Normal University, Shuqiang Li of the Institute of Zoology of the Chinese Academy of Sciences, Xin Zhao and Zhanqi Chen of the Key Laboratory of Tropical Forest Ecology at the Xishuangbanna Tropical Botanical Garden, and Haifeng Chen, also of the Hebei Key Laboratory of Animal Diversity at Langfang Normal University, describe two new species of Velvet Spider from Xinjiang Province, China.

Both new species are placed in the genus Eresus, which gives its name to the group and which contains 24 of the 102 currently described Velvet Spider species.

The first new species described is named Eresus da, where 'da' is a Chinese word meaning 'large', in reference to the large size of the species, the carapace of which can reach over 10 mm in length. Only a single female specimen of this species were observed, this being dark brown in colour, except for the carapace which is a lighter, reddish brown, and the white spots on the abdomen, the whole body being covered by short, white hairs.

Eresus da, holotype female. (A) Dorsal view. (B) lateral view. Lin et al. (2022).

The single known specimen of Eresus da was found living in a silk tunnel about 20 cm in length sheltered behind a clump of desert plants, and connected to an underground nest. The entrance to the tunnel was surrounded by the empty exoskeletons of desert Beetles, which appear to be the main prey of this species.

Eresus da, holotype female. (A) habitat; (B) microhabitat; (C) tunnel wrapped with Beetle exoskeletons; (D) Beetle skeletons (Pimeliinae sp.); (E) Spider with nest. Lin et al. (2022).

The second new species is named Ersus yukuni, in honour of Yu Kun, who collected the single known specimen of the species, a male. The specimen is black in colour, and covered by a dense layer of black and white hairs. 

Eresus kukuni, holotype male. (C) Dorsal view. (D) lateral view. Lin et al. (2022).

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Mammalian feeding traces on a Sauropod Dinosaur bone from the Late Jurassic of northwestern China.

For more than 160 million years, Mammals lived in the shadow of the Dinosaurs, remaining small and elusive with an average adult body size close to 100 g. Nonetheless, recent discoveries demonstrate that Mesozoic Mammals were ecologically diverse and occupied various ecological niches. They ranged from ground-dwelling generalists to specialists with semi-aquatic, fossorial, arboreal and even gliding habits. This ecological diversity suggests an equally varied diet, probably encompassing herbivory, insectivory, carnivory and omnivory. The reconstruction of the diet and feeding behaviour of Mesozoic Mammals is, however, largely based on circumstantial evidence such as tooth morphology. Direct evidence for feeding behaviour is scarce and so far limited to a stomach content from the Early Cretaceous, and four instances of feeding traces on bones from the Late Cretaceous. 

In a paper published in the journal The Science of Nature on 19 July 2020 Felix Augustin and Andreas Matzke of the Institut für Geowissenschaften at Eberhard Karls Universität Tübingen, Michael Maisch of Albstadt in Germany, and Juliane Hinz and Hans-Ulrich Pfretzschner, also of the Institut für Geowissenschaften at Eberhard Karls Universität Tübingen, describe bioerosional traces preserved on Dinosaur bone from the early Late Jurassic Qigu Formation (Oxfordian, approximately 160 million years old) of the southern Junggar Basin, northwestern China, and argue that they represent the oldest direct evidence of Mammalian feeding behaviour. This predates the hitherto oldest feeding traces ascribed to Mammals from the Late Cretaceous by more than 60 million years. Thus, these findings significantly expand our understanding of the ecology and behaviour of early Mammals.

The bioerosional traces were discovered on a bone fragment of a Sauropod Dinosaur at the northern flank of Liuhuanggou Gorge in the southern Junggar Basin of Xinjiang Province, northwestern China, approximately 40 km southwest of Urumqi. The locality was discovered during the Sino-German-Project in 2000, a joint expedition by the University of Tübingen, the Nanjing Institute for Geology and Palaeontology and the Geological Survey No. 1 of Xinjiang. The trace-bearing bone was associated with other fragmentary bones of a large-sized Mamenchisaurid Sauropod Dinosaur in a bone-bed horizon in the lower part of the Qigu Formation, approximately 50 m above the boundary with the underlying Toutunhe Formation. The Sauropod Dinosaur total length was estimated to be more than 20 m. Theropod teeth were found interspersed between the Sauropod remains and belong to a large-sized Carnosaur and a smaller Theropod of unknown affinities.

 

Map and stratigraphy of Liuhuanggou gorge. (a) Inset shows the position of the Junggar Basin (rectangle) within Xinjiang Province in northwestern China. (b) Geographic map of the Junggar Basin (Xinjiang Province, northwest China) and the position of Liuhuanggou gorge (asterisk). (c) 

Stratigraphy and sedimentology of the Toutunhe and Qigu Formation at the northern flank of Liuhuanggou gorge. The arrow marks the position of the Dinosaur bone-bed from which the bite marked bone was recovered. Augustin et al. (2020).

The Qigu Formation is early Late Jurassic in age and has a thickness of 680 m at Liuhuanggou Gorge. It consists of massive reddish mudstones and siltstones interbedded with fine-grained sandstone horizons. The sediments of the Qigu Formation were probably deposited on a low-gradient alluvial plain, composed of extensive floodplain areas, adjacent to braided river systems and slowflowing meandering rivers. Environmental conditions during the time of deposition have been interpreted as arid and highly seasonal. The diverse vertebrate fauna of the Qigu Formation thus far comprises Hybodont Sharks, Actinopterygian Fish, Temnospondyl Amphibians, Mammals, Xinjiangchelyid Turtles, Squamates and Choristoderes, Crocodylomorphs, Pterosaurs, as well as Sauropods, small and large Theropods, Stegosaurs and Ankylosaurs among Dinosaurs. The Mammal assemblage is particularly rich and comprises five different taxa: the Haramiyid Sineleutherus; two Docodonts, Tegotherium and Dsungarodon; the stem Zatherian Nanolestes; and an indeterminate Amphilestid Triconodont. All of these Mammals were found in a microvertebrate-bearing bone-bed at Liuhuanggou gorge close (300 m) to the Dinosaur bone-bed site. Stratigraphically, the Mammal site occurred only slightly higher (70 m) in the section, indicating that the Dinosaur and the Mammals lived more or less coeval in the same ecosystem.

The bioerosional traces are preserved on a fragmentary cervical rib of an indeterminate Mamenchisaurid Sauropod Dinosaur (SGP 2000/16). Although dozens of cervical rib fragments have been recovered from the Dinosaur site at Liuhuanggou, small bioerosional traces were only found on one bone fragment. Interestingly, the traces are limited to small ridges on the bone and do not occur on the more level or concave surfaces in between. They appear as elongated, shallow depressions that are restricted to the cortical bone and are principally arranged in parallel pairs. The traces are usually aligned opposite to each other, with one set of traces visible on one side of the ridge and the other set on the opposite side. The traces have a length of approximately 0.5–1.5 mm and a width of 30–250 μm.

 

Cervical rib of a Mamenchisaurid Sauropod (SGP 2000/16) from the lower Qigu Formation (Oxfordian, Late Jurassic) of Liuhuanggou gorge, northwestern China. (a) Overview photograph of the specimen (SGP 2000/16) displaying bioerosional traces. (b) Detail photograph of the bioerosional traces from a slightly different angle than in (a) for better visibility of the traces. (c) Detail photograph of the bioerosional traces from a slightly different angle than in (a) for better visibility of the traces. Augustin et al. (2020).

Small and elongated traces on bones have been linked to the following causes: trampling by large Vertebrates, feeding by Insects, and feeding by Vertebrates. Augustin et al. discuss all the possible trace-makers for the bioerosional traces and conclude that they were most likely produced by early Mesozoic Mammals. 

Trampling by large Vertebrates has often been inferred by the presence of small micro-striations on bone surfaces in fossil and sub-fossil settings. These micro-striations are much smaller, parallel and more uniform to one another, and are therefore different from the traces described by Augustin et al.

Insect traces are widespread in the fossil record and range in morphology from cavities and tunnels to star-shaped pits. Elongated grooves have also been ascribed to Insects, particularly Dermestid Beetles and Termites. The well-preserved traces from the Qigu Formation differ from these Insect feeding traces in having a teardrop shape, with one pointed and one blunt end. When several scratches occur as opposed parallel pairs, the blunt ends face each other. In these traces, the deepest part of the scratches is near the blunt end and not near the mid-length as it is the case in Termite traces. Additionally, Termite feeding traces often comprise star-shaped pits and are usually superimposed on one another, resulting in heavily bioeroded surfaces lacking most of the compact bone layer. Therefore, Augustin et al. conclude that Insects are not responsible for the traces.

Vertebrate feeding traces are frequently preserved on bones and usually come in the form of punctures, scores and grooves. The only Vertebrates from the Qigu Formation that fall within the size range of the traces described above are Mammals, as well as Squamates and one possible Choristoderan; however, the dentition pattern of Squamates and Choristoderans is incompatible with the arrangement of the bite marks described. Both possess a homodont dentitionwith closely packed and irregularly spaced teeth in the upper and lower jaw, and therefore, they cannot be the producer of these traces.

Mammals are the only Vertebrates that possess two sets of procumbent, paired incisors in the upper and lower jaw and can produce bite marks of the kind described. The Mammalian teeth recovered from Liuhuanggou mostly comprise molars and premolars that range in size from 0.5 to 1.5 mm. So far, only one incisor belonging to Sineleutherus uyguricus is known that has a cusp width of 200 μm and thus matches the size of the larger bite marks very well. For the other four taxa from this locality, unfortunately, incisors are unknown, but their estimated size lies well within the range expected from the traces. Moreover, the traces here described show all the characteristics of feeding traces ascribed to Mammals from the Late Cretaceous. 

Feeding traces by extant insectivorous Mammals described in the catalogue of vertebrate taphonomic identifications by Yolanda Fernández-Jalvo and Peter Andrews are almost identical to the ones described by Augustin et al., lending further support to the interpretation of Mammals as trace-makers. Interestingly, the bite marks of insectivorous Mammals more closely resemble the traces from Liuhuanggou than those of Rodents. This is expected because of the similarity of the dentition pattern and the reconstructed diet between extant insectivorous Mammals and the Mammals described from Liuhuanggou. Therefore, Augustin et al. contend that the feeding traces can be confidently assigned to Mammals based on the small size of the traces and their characteristic, paired arrangement with an opposing pair of bite marks preserved on the opposite side of ridges or protuberances.

Although the traces described herein are overall similar to bioerosional traces of insects, a thorough comparison with extant insectivore bite marks and accounts from the fossil record clearly indicates a Mammalian origin of the traces. In general, the interpretation of trace fossils, especially bioerosional traces, is often contentious and a matter of debate. However, Augustin et al. are confident that the most likely explanation of the bioerosional traces presented in their study is feeding activity by Mammals based on the typical arrangement in opposed pairs of some of the traces.

Due to the extreme size discrepancy of predator and prey, the bite marks clearly represent scavenging behaviour. Scavenging behaviour is expected in early Mammals because of their moderate dental complexity that allowed a generalized diet. Additionally, animal tissue provides a source for proteins, lipids and minerals that are otherwise hard to obtain for such small Animals with an estimated adult size of less than 100 g. Since the feeding traces are only superficially preserved on the bone  surface, they most likely were inflicted unintentionally during feeding. The arrangement of the bite marks along small ridges and the 'gnawed' appearance of the bone surface, points to selective feeding on the remaining soft tissues of the Dinosaur carcass that were still attached to the bones.

The Mammalian bite marks described by Augustin et al. represent the oldest direct evidence for a carnivorous diet in early Mammals. They also represent the oldest record of scavenging behaviour. Augustin et al.'s findings expand the known range of the early Mammalian feeding repertoire significantly and shed light on the palaeobiology and palaeoecology of early Mammals, a field that has been poorly known for a long time. Until now, there was a significant gap between the earliest known Mammals with a generalized heterodont dentition from the Late Triassic (220 million years ago) and the oldest feeding traces from the Late Cretaceous (100 million years ago). This study considerably reduces this gap.

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