Fragmentary Fossils Research Articles

Myoglobin primary structure reveals multiple convergent transitions to semi-aquatic life in the world's smallest mammalian divers.

The speciose mammalian order Eulipotyphla (moles, shrews, hedgehogs, solenodons) combines an unusual diversity of semi-aquatic, semi-fossorial, and fossorial forms that arose from terrestrial forbearers. However, our understanding of the ecomorphological pathways leading to these lifestyles has been confounded by a fragmentary fossil record, unresolved phylogenetic relationships, and potential morphological convergence, calling for novel approaches. The net surface charge of the oxygen-storing muscle protein myoglobin (ZMb), which can be readily determined from its primary structure, provides an objective target to address this question due to mechanistic linkages with myoglobin concentration. Here, we generate a comprehensive 71 species molecular phylogeny that resolves previously intractable intra-family relationships and then ancestrally reconstruct ZMb evolution to identify ancient lifestyle transitions based on protein sequence alone. Our phylogenetically informed analyses confidently resolve fossorial habits having evolved twice in talpid moles and reveal five independent secondary aquatic transitions in the order housing the world's smallest endothermic divers.

Early monk seals (Monachinae: Monachini) from the late Miocene–early Pliocene of Australia

Despite decades of research, the systematics of extinct true seals (Phocidae) is still overly reliant on morphological data from extant taxa. As a result, monk seals (Monachini) have been interpreted as ‘archaic’ despite an absence of fossil data to support this hypothesis. This has affected systematic hypotheses for extinct phocids, including fossils from Australasia. Recent finds from New Zealand indicate that the first seal fossils described from Australia, two temporal bones from the late Miocene–early Pliocene (6.24–4.35 Ma), need to be revisited. Here we re-describe these temporal bones and find them to represent monk seals. This places the oldest known fossils of this group in the Southern Hemisphere, implying monk seals had a longer history at southern latitudes. Our ancestral state estimation of the temporal bone morphology of monachines indicates that monk seal temporals may be derived, rather than plesiomorphic as has previously been assumed. This suggests that an over-reliance on the morphology of extant true seals may be obscuring the true diversity of both stem- and crown-phocids, and indicates that a rethink of the morphology underlying the taxonomic assessments of fragmentary true seal fossils is needed.

A fast-growing basal troodontid (Dinosauria: Theropoda) from the latest Cretaceous of Europe

A characteristic fauna of dinosaurs and other vertebrates inhabited the end-Cretaceous European archipelago, some of which were dwarves or had other unusual features likely related to their insular habitats. Little is known, however, about the contemporary theropod dinosaurs, as they are represented mostly by teeth or other fragmentary fossils. A new isolated theropod metatarsal II, from the latest Maastrichtian of Spain (within 200,000 years of the mass extinction) may represent a jinfengopterygine troodontid, the first reported from Europe. Comparisons with other theropods and phylogenetic analyses reveal an autapomorphic foramen that distinguishes it from all other troodontids, supporting its identification as a new genus and species, Tamarro insperatus. Bone histology shows that it was an actively growing subadult when it died but may have had a growth pattern in which it grew rapidly in early ontogeny and attained a subadult size quickly. We hypothesize that it could have migrated from Asia to reach the Ibero-Armorican island no later than Cenomanian or during the Maastrichtian dispersal events.

A three-dimensional approach to visualize pairwise morphological variation and its application to fragmentary palaeontological specimens.

Classifying isolated vertebrate bones to a high level of taxonomic precision can be difficult. Many of Australia’s Cretaceous terrestrial vertebrate fossil-bearing deposits, for example, produce large numbers of isolated bones and very few associated or articulated skeletons. Identifying these often fragmentary remains beyond high-level taxonomic ranks, such as Ornithopoda or Theropoda, is difficult and those classified to lower taxonomic levels are often debated. The ever-increasing accessibility to 3D-based comparative techniques has allowed palaeontologists to undertake a variety of shape analyses, such as geometric morphometrics, that although powerful and often ideal, require the recognition of diagnostic landmarks and the generation of sufficiently large data sets to detect clusters and accurately describe major components of morphological variation. As a result, such approaches are often outside the scope of basic palaeontological research that aims to simply identify fragmentary specimens. Herein we present a workflow in which pairwise comparisons between fragmentary fossils and better known exemplars are digitally achieved through three-dimensional mapping of their surface profiles and the iterative closest point (ICP) algorithm. To showcase this methodology, we compared a fragmentary theropod ungual (NMV P186153) from Victoria, Australia, identified as a neovenatorid, with the manual unguals of the megaraptoran Australovenator wintonensis (AODF604). We discovered that NMV P186153 was a near identical match to AODF604 manual ungual II-3, differing only in size, which, given their 10–15Ma age difference, suggests stasis in megaraptoran ungual morphology throughout this interval. Although useful, our approach is not free of subjectivity; care must be taken to eliminate the effects of broken and incomplete surfaces and identify the human errors incurred during scaling, such as through replication. Nevertheless, this approach will help to evaluate and identify fragmentary remains, adding a quantitative perspective to an otherwise qualitative endeavour.

The fossil record of the ocelot Leopardus pardalis (Carnivora, Felidae): a new record from the southern range of its distribution and its paleoenvironmental context

ABSTRACT Leopardus is a genus that, despite currently being widely distributed in South America, shows until now a fragmentary fossil record. Among Leopardus, L. pardalis is the largest species, having an historical range that includes tropical and subtropical habitats from southern U.S.A. to southern South America but, as usual in the ocelot lineage, fossil remains that can be interpreted with certainty are restricted to the Late Pleistocene of southern U.S.A. and Brazil. Here we present a new record (a fragment of right maxillary plus zygomatic with P4–M1; incomplete left mandible with the coronoid process, part of c1 alveolus and p3–m1; isolated right c1) from the Late Pleistocene of Arroyo Toropí, Corrientes province, Argentina. The bearing level was dated with Optically Stimulated Luminescence (OSL) to 98.4 ka (Marine Isotopic Stage, MIS 5c). Present environmental requirements of L. pardalis and climatic reconstructions carried out here suggest a compatible scenario with MIS 5 for this fossil, which is concordant with the associated dating (ca. 98.4 ka). Leopardus pardalis appears to be part of a subtropical fauna, with Tayassu pecari and Euphractus sexcinctus, which inhabited the region during warm and wet climatic events of MIS 5c. Phytoliths and other vertebrates are congruent with its presence, since the inferred conditions are similar to the present one. The new record is relevant not only because it is the first fossil record of the species for the Pleistocene of Argentina, but also because it is placed 1800 km south of the closest accurately identified published fossil.

Is the middle cranial fossa a reliable predictor of temporal lobe volume in extant and fossil anthropoids?

We investigate the suitability of middle cranial fossa (MCF) size as a proxy for temporal lobe volume (TLV), examining the strength of the association between TLV and MCF metrics and assess the reliability predicting TLV in fossil anthropoids. The temporal lobe of the primate brain is a multimodal association cortex involved in long-term memory, auditory, and visual processing with unique specializations in modern humans for language comprehension. The MCF is the bony counterpart for the temporal lobe providing inferences for fossil hominin temporal lobe evolution. We now investigate whether the MCF is a suitable proxy for the temporal lobe. A sample of 23 anthropoid species (n = 232, including 13 fossil species) from computed tomography (CT) scans of ex vivo crania and magnetic resonance imaging (MRI) of the in vivo brain were generated into three-dimensional (3D) virtual models. Seven linear metrics were digitally measured on the right MCF with right TLV calculated from in vivo MRI. Regression analyses produced statistically significant correlations between TLV and all MCF metrics (r ≥ 0.85; p ≤ 0.0009) with TLV predictions within ±1 standard error and three MCF metrics (posterior-width, mid-length, and mid-width) the most reliable predictors of TLV with only one metric weakly associated with TLV. These findings indicate a strong association between the MCF and TLV, provide reliable predictors of fossil TLV that were previously unattainable, allow the inclusion of fragmentary fossil material, and enable inferences into the emergence of modern human temporal lobe morphology.

Phylogenetic Implications of Dental Characters in Henricosborniidae (Mammalia, Notoungulata)

Henricosborniids are a group of South American native ungulates mainly found in Argentina (several Patagonian localities, Jujuy, and Mendoza), Brazil (São José de Itaboraí), and Bolivia (Tiupampa) that have a biochron ranging from the Danian (Tiupampan SALMA) to the late Bartonian (Barrancan subage of the Casamayoran SALMA). The record of henricosborniids in Mustersan levels must be confirmed. The family includes the genera Henricosbornia, Peripantostylops, Othnielmarshia, Orome, and Simpsonotus. Their fragmentary fossil record, mainly limited to isolated teeth, has constrained their utility for obtaining phylogenetically useful characters; for that reason, only few taxa (i.e., Henricosbornia, Simpsonotus) are usually included in this type of analysis. Even though there is consensus about the basal position of the group within the order, the family is recovered as polyphyletic or, more commonly, paraphyletic. The analysis of specimens from the early Eocene of Las Violetas and Las Flores (Itaboraian SALMA), the oldest Patagonian localities yielding notoungulate remains, and Paso del Sapo, along with the implementation of both implied weighting and landmark information, allow us to discuss several features for use in henricosborniid phylogenetic analysis and identification: 1) ectoloph of the molars with well-marked paracone and metacone folds; 2) molars with crochet present, oblique to the ectoloph, with variable development; 3) triangular third upper molar, with poorly developed hypocone; 4) reduced trigonid with short paralophid; 5) entoconid more like an isolated cusp and not completely crested. Although useful, these characters need to be evaluated in a more exhaustive phylogenetic context.

A new genus and species of sabretooth, Oriensmilus liupanensis (Barbourofelinae, Nimravidae, Carnivora), from the middle Miocene of China suggests barbourofelines are nimravids, not felids

Since the early 2000s, a revival of a felid relationship for barbourofeline sabretooths has become popular due to recent discoveries of fragmentary fossils from Africa. According to this view, barbourofelines trace their common ancestor with felids through shared similarities in dental morphology going back to the early Miocene of Africa and Europe. However, whether or not such an idea is represented in the basicranial morphology, a conservative area of high importance in family-level relationships, is yet to be tested. A nearly complete skull of Oriensmilus liupanensis gen. and sp. nov. from the middle Miocene Tongxin Basin of northern China represents the most primitive known barbourofeline with an intact basicranial region, affording an opportunity to re-examine the relationship of felids and nimravines. We also present an update on East Asian records of barbourofelines. The new skull of Oriensmilus possesses a suite of characters shared with nimravines, such as the lack of an ossified (entotympanic) bullar floor, absence of an intrabullar septum, lack of a ventral promontorial process of the petrosal, presence of a small rostral entotympanic on the dorsal side of the caudal entotympanic, and a distinct caudal entry of the internal carotid artery and nerve that pierces the caudal entotympanic at the junction of the ossified and unossified caudal entotympanics. The absence of an ossified bullar floor in O. liupanensis and its presence in those from the middle Miocene of Sansan, France thus help to bracket the transition of this character, which must have happened in the early part of the middle Miocene. Spatial relationships between bullar construction and the middle ear configuration of the carotid artery in Oriensmilus strongly resemble those in nimravines but are distinctly different from felids and other basal feliforms. Despite the attractive notion that early barbourofelines arose from a Miocene ancestor that also gave rise to felids, the basicranial evidence argues against this view.http://zoobank.org/urn:http://lsid:zoobank.org:pub:2DE98DBC-4D02-4E18-9788-0B0D8587E73F

Paleoenvironmental context and significance of a partial elasmosaurid skeleton from the Albian of Haute-Provence, France

The Early–Late Cretaceous transition (late Albian–early Cenomanian; ~100 Ma) witnessed marked environmental changes and a deep reorganization of the marine fauna. The impact of these environmental and biotic changes on Tethyan marine vertebrates is poorly understood, due to a fragmentary fossil record. Here we report upper Albian marine vertebrate remains, including a partially articulated plesiosaurian skeleton, from a fossiliferous glauconite-rich bed in the Alpes de Haute-Provence, France. The fossiliferous horizon produced a diversified invertebrate fauna including ammonoids and belemnoids. The ammonite fauna is abundant and diversified, indicating the Mortoniceras fallax ammonite Zone. The calcareous nannofossil biomarkers date the bed to the NC10a Zone. The fossiliferous bed consists of glauconitic marls enriched in planktic foraminifera and occurs amongst a monotonous succession of alternating marlstones and limestone beds. The vertebrate fauna consists of chondrichthyans and marine reptiles. Chondrichthyans are represented by five Lamniformes species (dominated by Sphenodus) and comprise predator taxa probably living in open marine temperate waters. The site yielded a large, partial post-cranial plesiosaurian skeleton with articulated elements, belonging to an elasmosaurid and representing one of the most complete Albian plesiosaurian specimens known from Europe. The abundance and preservation of the collected fossil remains are best explained by their concentration during a basin-scale episode of very low sedimentation corresponding to a major episode of marine transgression, associated with a lower oxygenation of bottom waters. These findings indicate that the newly discovered fossiliferous bed holds promising clues about the evolutionary history of major groups of marine vertebrates and ammonites near the Early–Late Cretaceous transition.

The morphological diversity of the quadrate bone in squamate reptiles as revealed by high-resolution computed tomography and geometric morphometrics.

We examined the morphological diversity of the quadrate bone in squamate reptiles (i.e. lizards, snakes, amphisbaenians). The quadrate is the principal splanchnocranial element involved in suspending the lower jaw from the skull, and its shape is of particular interest because it is potentially affected by several factors, such as phylogenetic history, allometry, ecology, skull kinesis and hearing capabilities (e.g. presence or absence of a tympanic ear). Due to its complexity, the quadrate bone is also considered one of the most diagnostic elements in fragmentary fossil taxa. We describe quadrates from 38 species spread across all major squamate clades, using qualitative and quantitative (e.g. geometric morphometrics) methods. We test for possible correlations between shape variation and factors such as phylogeny, size, ecology and presence/absence of a tympanum. Our results show that the shape of the quadrate is highly evolutionarily plastic, with very little of the diversity explained by phylogenetic history. Size variation (allometric scaling) is similarly unable to explain much shape diversity in the squamate quadrate. Ecology (terrestrial/fossorial/aquatic) and presence of a tympanic ear are more significant, but together explain only about 20% of the diversity observed. Other unexplored and more analytically complex factors, such as skull biomechanics, likely play additional major roles in shaping the quadrates of lizards and snakes.

Fossil dragonflies (Odonata: Anisoptera) from the early Eocene Okanagan Highlands, western North America

AbstractWe describe the first dragonflies (Odonata: Anisoptera) from the early Eocene Okanagan Highlands of far-western North America from nine fossils. Six are assigned to five species in four new, named genera of Aeshnidae:Antiquiala snyderaenew genus and species,Idemlinea versatilisnew genus and species,Ypshna brownleeinew genus and species,Ypshna latipennatanew genus and species, andEoshna thompsonensisnew genus and species; we treat one as Aeshnidae genus A, species A; one is assigned to Gomphidae:Auroradraco eosnew genus and species; and we treat a ninth, fragmentary fossil of unknown family affinity as Anisoptera indeterminate genus A, species A, which represents a seventh genus and eighth species. The dominance of Aeshnidae is consistent with other Paleocene and Eocene fossil localities.Auroradraco eosis the only fossil Gomphidae in the roughly 66-million-year gap between occurrences in mid-Cretaceous Burmese amber and the early Oligocene of France.Ypshnaappears close toParabaissaeshna ejerslevensefrom the early Eocene Fur Formation of Denmark; this is not surprising given Holarctic intercontinental connections at this time and a growing list of insect taxa shared between the Okanagan Highlands and the Fur Formation.

Hominin and animal activities in the microstratigraphic record from Denisova Cave (Altai Mountains, Russia)

Denisova Cave in southern Siberia uniquely contains evidence of occupation by a recently discovered group of archaic hominins, the Denisovans, starting from the middle of the Middle Pleistocene. Artefacts, ancient DNA and a range of animal and plant remains have been recovered from the sedimentary deposits, along with a few fragmentary fossils of Denisovans, Neanderthals and a first-generation Neanderthal–Denisovan offspring. The deposits also contain microscopic traces of hominin and animal activities that can provide insights into the use of the cave over the last 300,000 years. Here we report the results of a micromorphological study of intact sediment blocks collected from the Pleistocene deposits in the Main and East Chambers of Denisova Cave. The presence of charcoal attests to the use of fire by hominins, but other evidence of their activities preserved in the microstratigraphic record are few. The ubiquitous occurrence of coprolites, which we attribute primarily to hyenas, indicates that the site was visited for much of its depositional history by cave-dwelling carnivores. Microscopic traces of post-depositional diagenesis, bioturbation and incipient cryoturbation are observed in only a few regions of the deposit examined here. Micromorphology can help identify areas of sedimentary deposit that are most conducive to ancient DNA preservation and could be usefully integrated with DNA analyses of sediments at archaeological sites to illuminate features of their human and environmental history that are invisible to the naked eye.

Reconstructing birth in Australopithecus sediba

Hominin birth mechanics have been examined and debated from limited and often fragmentary fossil pelvic material. Some have proposed that birth in the early hominin genus Australopithecus was relatively easy and ape-like, while others have argued for a more complex, human-like birth mechanism in australopiths. Still others have hypothesized a unique birth mechanism, with no known modern equivalent. Preliminary work on the pelvis of the recently discovered 1.98 million-year-old hominin Australopithecus sediba found it to possess a unique combination of Homo and Australopithecus-like features. Here, we create a composite pelvis of Australopithecus sediba to reconstruct the birth process in this early hominin. Consistent with other hominin species, including modern humans, the fetus would enter the pelvic inlet in a transverse direction. However, unlike in modern humans, the fetus would not need additional rotations to traverse the birth canal. Further fetal rotation is unnecessary even with a Homo-like pelvic midplane expansion, not seen in earlier hominin species. With a birth canal shape more closely associated with specimens from the genus Homo and a lack of cephalopelvic or shoulder constraints, we therefore find evidence to support the hypothesis that the pelvic morphology of Australopithecus sediba is a result of locomotor, rather than strictly obstetric constraints.

A late middle pleistocene Denisovan mandible from the Tibetan Plateau

Denisovans are members of a hominin group who are currently only known directly from fragmentary fossils, the genomes of which have been studied from a single site, Denisova Cave1–3 in Siberia. They are also known indirectly from their genetic legacy through gene flow into several low-altitude East Asian populations4,5 and high-altitude modern Tibetans6. The lack of morphologically informative Denisovan fossils hinders our ability to connect geographically and temporally dispersed fossil hominins from Asia and to understand in a coherent manner their relation to recent Asian populations. This includes understanding the genetic adaptation of humans to the high-altitude Tibetan Plateau7,8, which was inherited from the Denisovans. Here we report a Denisovan mandible, identified by ancient protein analysis9,10, found on the Tibetan Plateau in Baishiya Karst Cave, Xiahe, Gansu, China. We determine the mandible to be at least 160 thousand years old through U-series dating of an adhering carbonate matrix. The Xiahe specimen provides direct evidence of the Denisovans outside the Altai Mountains and its analysis unique insights into Denisovan mandibular and dental morphology. Our results indicate that archaic hominins occupied the Tibetan Plateau in the Middle Pleistocene epoch and successfully adapted to high-altitude hypoxic environments long before the regional arrival of modern Homo sapiens. Fossil evidence indicates that Denisovans occupied the Tibetan Plateau in the Middle Pleistocene epoch and successfully adapted to this high-altitude hypoxic environments long before the regional arrival of modern Homo sapiens.

The variability of frontal and occipital features of Homo erectus: a comparative analysis of unpublished fragmentary fossils from Sangiran, Indonesia

Since the first publication of Dubois in 1894, the diagnosis of Homo erectus is based on a list of morphological features established and updated after successive major discoveries made in the 20th century. While the existence and limits of the Homo erectus s.l is still debated, the homogeneity of the Indonesian Homo erectus, which covers a chronological period of ca. 1.5 million years, is also regularly questioned. Most of the studies addressing this question remain focused on the few most preserved specimens, even if a significant number of fragmentary specimens are available which could help to better appreciate the morphological variability of this species. In this present analysis, several unpublished fragmentary frontal (n=6) and occipital (n=9) bones recovered from the Pucangan and Kabuh layers in the Sangiran dome (Central Java) are described, analyzed and compared to the 3D models of contemporaneous (Trinil, Sangiran) and younger (Solo series) Indonesian H. erectus, specimens from Zhoukoudian Lower Cave in China, Dmanisi (Georgia), as well as East African hominins (East and West Turkana, Olduvai). The results help to precise the anatomical characteristics of these isolated human remains and increase our knowledge of Javanese Homo erectus morphological variability.

The oldest short-tailed whipscorpion (Schizomida): A new genus and species from the Upper Cretaceous amber of northern Myanmar

Arachnids are an ancient lineage of arthropods and orders such as scorpions, harvestmen and mites have their fossil origins in the Silurian or Devonian. Another order with potentially old origins is the short-tailed whipscorpions, or schizomids (Arachnida: Schizomida). These animals have a fragmentary fossil record with species either described or documented from Dominican amber (Miocene: Chattian), drill core sediments from the Oligocene in China, and the upper Pliocene (Zanclean) of Arizona. Here, we describe the first named example of a short-tailed whipscorpion from Upper Cretaceous amber (Myanmar: Hukawng Valley) based on male morphological features. Mesozomus groehni gen. et sp. n. cannot be assigned to any Recent genera of schizomids and preserves a unique mix of plesiomorphic (e.g. the retention of eyes) and apomorphic characters (e.g. enlarged femur IV) that merit future evaluation within a phylogenetic context. We extend the fossil record of schizomids by ca. 65 million years, from the Paleogene to the Mesozoic, and add the twelfth order of arachnids to the diverse arachnid biota documented from Burmese amber.

A late Middle Pleistocene Denisovan mandible from the Tibetan Plateau

Denisovans are members of a hominin group who are currently only known directly from fragmentary fossils, the genomes of which have been studied from a single site, Denisova Cave1-3 in Siberia. They are also known indirectly from their genetic legacy through gene flow into several low-altitude East Asian populations4,5 and high-altitude modern Tibetans6. The lack of morphologically informative Denisovan fossils hinders our ability to connect geographically and temporally dispersed fossil hominins from Asia and to understand in a coherent manner their relation to recent Asian populations. This includes understanding the genetic adaptation of humans to the high-altitude Tibetan Plateau7,8, which was inherited from the Denisovans. Here we report a Denisovan mandible, identified by ancient protein analysis9,10, found on the Tibetan Plateau in Baishiya Karst Cave, Xiahe, Gansu, China. We determine the mandible to be at least 160thousand years old through U-series dating of an adhering carbonate matrix. The Xiahe specimen provides direct evidence of the Denisovans outside the Altai Mountains and its analysis unique insights into Denisovan mandibular and dental morphology. Our results indicate that archaic hominins occupied the Tibetan Plateau in the Middle Pleistocene epoch and successfully adapted to high-altitude hypoxic environments long before the regional arrival of modern Homo sapiens.

Description of new dyrosaurid specimens from the Late Cretaceous–Early Paleogene of New Jersey, United States, and comments on Hyposaurus systematics

ABSTRACT Dyrosauridae was a successful clade of marine crocodyliforms that survived the Cretaceous–Paleogene biotic crises. The most important taxon from North America is Hyposaurus rogersii, a species first described in the mid-19th century based on fragmentary fossils. Several new specimens are described here, comprising material that once belonged to the Yale Peabody Museum (New Haven, USA) but obtained later by L.I. Price and housed in the paleontological collections of the former Divisão de Geologia e Mineralogia (Rio de Janeiro, Brazil). The remains include postcranial bones and fragments of a lower jaw. The present work urges for the necessity of a revision about the validity of Hyposaurus rogersii based on the absence of diagnostic features observed in the holotype. The new specimens show new postcranial features that support the importance of the postcranial bones for dyrosaurid systematics.

The sinemydid turtle Ordosemys from the Lower Cretaceous Mengyin Formation of Shandong, China and its implication for the age of the Luohandong Formation of the Ordos Basin.

Chronostratigraphic correlation of terrestrial Early Cretaceous biotas in China is highly problematic due to the lack of marine deposits, few absolute dates, and limited number of index fossils. This often leaves vertebrate faunas as one of the few potential tools for a preliminary biostratigraphy. Taxonomic identity of fragmentary fossils is, however, often uncertain and many faunas are insufficiently sampled. Turtles are one of the most common elements of Early Cretaceous biotas of Asia and their skeleton is frequently preserved more completely than that of other vertebrates- they yet receive little attention from vertebrate paleontologists. We here record the presence of the sinemydid turtle Ordosemys leios from the Lower Cretaceous Mengyin Formation of Shandong Province, China, best known for the first dinosaurs and Mesozoic turtles described from the country. Ordosemys is the third turtle reported from the Mengyin Formation along with Sinemys lens and Sinochelys applanata and the only other formation where Ordosemys is known to co-occur with Sinemys is the Luohandong Formation of the Ordos Basin (Inner Mongolia), the type and so far only horizon of Ordosemys leios. The presence of the crocodyliform Shantungosuchus may further define a fauna that is so far only known from these two formations. The stratigraphic position of the Luohandong Formation is poorly controlled and it has been placed anywhere between the Valanginian and Aptian. Published absolute dates from the Mengyin Formation and the numerous shared vertebrate and invertebrate taxa (now also including turtles) implies a Valanginian—early Hauterivian age for the Luohandong Formation—in contrast to late Hauterivian-Albian as previously proposed using the temporal distribution of Psittacosaurus. The new specimen of Ordosemys leios preserves the only known manus of this species and ecomorphological analysis of limb proportions implies that it was a less capable swimmer compared to Ordosemys liaoxiensis coming from the younger Jehol Biota.

Human teeth from securely stratified Middle Stone Age contexts at Sibudu, South Africa

The fossil record of early Homo sapiens in the African Pleistocene remains sparse. In contrast to its prominent position regarding the cultural evolution of our species, southern Africa plays a secondary role in narratives regarding human biological origins. Reasons for this are a limited and fragmentary fossil record from the Middle Stone Age (MSA), further complicated by a number of human remains coming from contexts lacking chronostratigraphic information. Similar to the southern African MSA overall, the rich archeological deposits of Sibudu stand in opposition to its scarce record of hominin fossils. Here, we report on three human teeth (SIB-1, 2, 3) from securely stratified MSA deposits at Sibudu dating between > 77 and 64 ka. The teeth include two lower deciduous molars (Ldm2) with heavy occlusal wear and one fragment. We focus on describing the find and archeological context, followed by an initial assessment of the fossils and their contextualization within the African record. The juvenile teeth derive from rich and well-stratified archeological deposits, associated with a Howiesons Poort industry at ~ 64 ka from PGS3 (SIB-3) and pre-Still Bay occupations in strata Casper and Danny at > 77 ka (SIB-1, 2). The latter constitute the oldest human fossils from Sibudu. Metric and morphological analyses of the Ldm2s (SIB-2, 3) find a combination of archaic traits (e.g., mid-trigonid crest) and crown dimensions that overlap with ranges of both Pleistocene and recent Homo sapiens. These results match with a population of Homo sapiens that lies chronologically between the earliest members of the species and recent humans.