The tribe Machairodontini is a major lineage of felid sabertooth cats that flourished in the late Cenozoic and included the top predators in the ecosystem of that time. As top predators members of ...the tribe had a profound influence on the paleoenvironment, yet the evolution and diversification of this tribe are unclear due to a lack of comprehensive revision and phylogenetic study. Here we describe a new dwarfed ecomorph of Machairodontini, Taowu liui gen. et sp. nov., from the Early Pleistocene of northern China, and carry out the best sampled phylogeny of the subfamily to date. Our analyses support that the African Mio-Pleistocene Lokotunjailurus represents an early divergent group, convergent with the Amphimachairodus-Homotheriina lineage in dental traits. The derived Pliocene to Pleistocene subtribe Homotheriina originated in Africa, from Adeilosmilus gen. nov. kabir or very a closely related taxon. Taowu liui gen. et sp. nov. belongs to a sister clade to Homotheriina. The Plio-Pleistocene Homotheriina of the New World belong to a monophyletic group in which Ischyrosmilus-Xenosmilus show a gradual adaptation to handling slow and powerful prey, whereas the true Homotherium only appeared after the Middle Pleistocene, in a separate intercontinental dispersal event.
•The first systematic phylogeny sabertooth.•A new form Taowu liui gen. et sp. nov. found from Pleistocene of North China.•Derived Plio-Pleistocene members of Machairodontini, here proposed name Homotheriina, origianated in African Adeilosmilus gen. nov.•Homotheriina dispersed to North America at least two times.
A central premise of bioclimatic envelope modeling is the assumption of niche conservatism. Whereas such assumptions are testable in modern populations, it is unclear whether niche conservatism holds ...over deeper time spans and over very large geographic ranges. Hyaenids occupied a diversity of ecological niches over time and space, and until the end-Pleistocene they occurred in Europe and most of Asia, with Asian populations of Crocuta suggested as being genetically distinct from their closest living relatives. Further, little is known regarding whether and how the dietary ecology of extinct populations of Crocuta differed from those of their extant African counterparts. Here, we use a multiproxy approach to assess an assumption of conserved dietary ecology in late Pleistocene extant spotted hyenas via finite element analysis, dental microwear texture analysis, and a novel dental macrowear method (i.e., whether teeth are minimally, moderately, or extremely worn, as defined by degree of dentin exposure) proposed here. Results from finite element simulations of the masticatory apparatus of Chinese and African Crocuta demonstrate lower skull stiffness and higher stress in the orbital region of the former when biting with carnassial teeth, suggesting that Chinese Crocuta could not process prey with the same degree of efficiency as extant Crocuta crocuta. Dental microwear texture data further support this interpretation, as Chinese Crocuta have intermediate and indistinguishable complexity values (indicative of hard-object feeding) between the extant African lion (Panthera leo) and extant hyenas (C. crocuta, Hyaena hyaena, and Parahyaena brunnea), being most similar to the omnivorous P. brunnea. The use of dental macrowear to infer dietary behavior may also be possible in extinct taxa, as evinced by dietary correlations between extant African feliforms and dental macrowear assignments. Collectively, this multiproxy analysis suggests that Chinese Crocuta may have exhibited dietary behavior distinct from that of living C. crocuta, and assumptions of niche conservatism may mask significant dietary variation in species broadly distributed in time and space.
Fossils of the ursid
Indarctos
from Withlacoochee River 4A of Florida (late early Hemphillian North American Land Mammal Age, Hh2, ~ 7.5–6.5 Ma) represent the best sample of this genus in North ...America, including both craniodental and postcranial specimens, yet only the skull has been described. In this study, we describe the other material of this bear from the same locality and review the records of
Indarctos
in North America.
Indarctos
from Withlacoochee River 4A has dental characters in accordance with those of typical
Indarctos oregonensis
, but has distinctly more slender postcranial bones.
Indarctos
from other localities of North America contains two morphs with regards to postcranial robustness, but lacks a clear geographic pattern.
Indarctos
from Withlacoochee River 4A shares traits with the Old World
Indarctos zdanskyi
and may be its descendant in the New World. The machairodont from Withlacoochee River 4A shows typical characters (e.g., presence of distinct P4 preparastyle and mandibular flange) that allow referral to
Amphimachairodus
rather than to
Nimravides
. Its morphology also shows a stronger affinity of this population to the Old World
Amphimachairodus horribilis
rather than to Hh3
Amphimachairodus coloradensis
. Previously, most North American records of
Amphimachairodus
were late Hemphillian (Hh3–4, ~ 6.5–4.5 Ma), when it co-occurred with a different ursid, “
Agriotherium.
” The Withlacoochee River 4A specimens provide evidence that
Amphimachairodus
dispersed from Asia during the Hh2. The special morphology of
Indarctos
and the presence of
Amphimachairodus
in a Hh2 fauna suggest that the environment had begun to change before the significant fauna turnover between the early and late Hemphillian.
The iconic sabretooth
is thought to have hunted cooperatively, but the origin of this behaviour and correlated morphological adaptations are largely unexplored. Here we report the most primitive ...species of
(
sp. nov.), a member of Machairodontini basal to
, from the Linxia Basin, northeastern border of the Tibetan Plateau (9.8-8.7 Ma). The long snout, laterally oriented and posteriorly located orbit of
suggest a better ability to observe the surrounding environment, rather than targeting single prey, pointing to an adaptation to the open environment or social behaviour. A pathological forepaw of
provides direct evidence of partner care. Our analyses of trait evolutionary rates support that traits correlated with killing behaviour and open environment adaptation evolved prior to other traits, suggesting that changes in hunting behaviour may be the major evolutionary driver in the early evolution of the lineage.
represents one of the most important transitions in the evolution of Machairodontini, leading to adaptation in open environments and contributing to their further dispersal and radiation worldwide. This rapid morphological change is likely to be correlated with increasingly arid environments caused by the rise of the Tibetan Plateau, and competition from abundant large carnivores in this area.
For a long time, it is controversial whether cave bears have ever lived in China during the Pleistocene. Here we checked the published and unpublished bear fossils from Zhoukoudian (North China) ...housed in Institute of Vertebrate Paleontology and Palaeoanthropology, CAS and Zhoukoudian Site Museum, and compared them with contemporary cave bears and brown bears. Our observation confirms the existence of cave bears only in Loc. 1 of Zhoukoudian. The general morphology of cave bears in China is similar to that of the early Middle Pleistocene cave bears in Europe and this bear can be assigned to Ursus deningeri. The metacarpals of U. deningeri from Loc. 1 of Zhoukoudian are much plumper than those of the approximately contemporary U. deningeri from Hundsheim (Austria) and are similar to those of the Late Pleistocene U. spelaeus/ingressus, presumably with a good digging ability. In contrast to Europe and Caucasus, cave bears from China are much less abundant than brown bears during the Middle Pleistocene.
•Cave bear presence in China was unambiguously confirmed for the first time.•Some newly defined characters distinguishing brown bears and cave bears were developed.•First systematic revision of fossil bear from Zhoukoudian allows to indicate time span of cave bear records in China.
The long-trunked elephantids underwent a significant evolutionary stage characterized by an exceptionally elongated mandible. The initial elongation and subsequent regression of the long mandible, ...along with its co-evolution with the trunk, present an intriguing issue that remains incompletely understood. Through comparative functional and eco-morphological investigations, as well as feeding preference analysis, we reconstructed the feeding behavior of major groups of longirostrine elephantiforms. In the Platybelodon clade, the rapid evolutionary changes observed in the narial region, strongly correlated with mandible and tusk characteristics, suggest a crucial evolutionary transition where feeding function shifted from the mandible to the trunk, allowing proboscideans to expand their niches to more open regions. This functional shift further resulted in elephantids relying solely on their trunks for feeding. Our research provides insights into how unique environmental pressures shape the extreme evolution of organs, particularly in large mammals that developed various peculiar adaptations during the late Cenozoic global cooling trends.
New material of
Agriotherium
from the late Hemphillian (~6 Ma) Quiburis Formation in Arizona, North America is reported. These specimens represent a new species,
Agriotherium hendeyi
, sp. nov., of ...small size and with a bucco-lingually narrow lower dentition distinguishing it from North American “
Agriotherium
”
schneideri
as well as the genotype and other Old World species of
Agriotherium
. Strikingly, the m1 metaconid-entoconid complex of the new species exhibits a morphologically transitional state between the pattern observed in
Indarctos
(three cusps) and the typical
Agriotherium
pattern (two cusps). Together with a review of the variation in
A. africanum
, a geometric morphometric analysis permits identification and discussion of a proposed transformation pathway from the
Indarctos
pattern to the
Agriotherium
pattern. It is shown that the two cusps in the metaconid-entoconid complex in
Agriotherium
correspond to the two entoconids in
Indarctos
, whereas the ancestral metaconid is reduced or lost in
Agriotherium
. From a developmental perspective, the metaconid fused to the anterior entoconid as a result of the shortening of the talonid, rather than via replacement of the metaconid by a posterior shift of the entoconid, presumably under selective pressure towards a more typically hypercarnivorous tooth morphology and carnivorous diet.
The accumulation of large datasets and increasing data availability have led to the emergence of data-driven paleontological studies, which reveal an unprecedented picture of evolutionary history. ...However, the fast-growing quantity and complication of data modalities make data processing laborious and inconsistent, while also lacking clear benchmarks to evaluate data collection and generation, and the performances of different methods on similar tasks. Recently, artificial intelligence (AI) has become widely practiced across scientific disciplines, but not so much to date in paleontology where traditionally manual workflows have been more usual. In this study, we review >70 paleontological AI studies since the 1980s, covering major tasks including micro- and macrofossil classification, image segmentation, and prediction. These studies feature a wide range of techniques such as Knowledge-Based Systems (KBS), neural networks, transfer learning, and many other machine learning methods to automate a variety of paleontological research workflows. Here, we discuss their methods, datasets, and performance and compare them with more conventional AI studies. We attribute the recent increase in paleontological AI studies most to the lowering of the entry bar in training and deployment of AI models rather than innovations in fossil data compilation and methods. We also present recently developed AI implementations such as diffusion model content generation and Large Language Models (LLMs) that may interface with paleontological research in the future. Even though AI has not yet been a significant part of the paleontologist's toolkit, successful implementation of AI is growing and shows promise for paradigm-transformative effects on paleontological research in the years to come.
•First systematic review of artificial intelligence (AI) applications in paleontology.•There has been a 20-year delay in data set scale in paleontology, and a 10-year delay in model implementation.•Recent progress in paleontological AI studies is likely a result of lowering bar in model construction and training.•Future directions for interactions between paleontology and AI are discussed.
Canis mosbachensis is a widely distributed species from the Early to Middle Pleistocene in Europe. In Eastern Asia, Canis variabilis was supposed to be a local subspecies of C. mosbachensis, but such ...hypothesis has never been tested in details. Here we restudied the Canis materials from type locality, Loc.1 of ZKD (Zhoukoudian) of Middle Pleistocene, as well as other localities that produced important materials of this taxon (e.g. Loc.13 of ZKD). To better evaluate the variability of the Pleistocene Canis, a series of morphotypes are described. Based on morphotype and morphometric, the present study reveals there is only one species present at Loc.1 and Loc.13 of ZKD, which is quite similar to European C. mosbachensis and should be revised as a subspecies of C. mosbachensis, namely C. mosbachensis variabilis. C. m. variabilis is more derived and less hypercarnivorous than the Early Pleistocene Canis chihliensis (as well as European Canis etruscus and Canis arnensis) in craniodental characters, whereas it is less derived and less hypercarnivorous than Canis lupus. A review of fossil records of C. m. variabilis in China was made based on these different characters. Canids from Gongwangling, Lantian of Shaanxi Province (middle or late Early Pleistocene) are the earliest known representatives of C. mosbachensis in China, which are still more primitive than C. m. variabilis from the Middle Pleistocene sites of ZKD. Reliable records of C. mosbachensis are only known from the Early Pleistocene to the late Middle Pleistocene in Northern China. C. m. variabilis is not direct ancestor to C. lupus but a close relative of the latter, while it is far from the Early Pleistocene C. chihliensis. The latter remains more primitive characters that are more similar to those of European Canis etruscus and Canis arnensis.
The East Asian records of Amphicyon are rare, fragmented, and unclear. Heretofore, no material could be definitely assigned to this genus. Here, we report a maxillary fragment with P4–M2 and the M3 ...alveolus from the early middle Miocene Dingjia'ergou fauna, Tongxin, northern China. The enlarged and anteroposteriorly elongated M2 clearly allows us to assign the specimen to Amphicyon as Amphicyon zhanxiangi, sp. nov. The new species is closest to European A. giganteus (e.g., presence of the parastyle and a posteriorly located protocone of P4) and represents an immigrant from Europe during the late early or the earliest middle Miocene. The morphological differences between Amphicyon zhanxiangi, Amphicyon ulungurensis, and North American Amphicyon species suggest at least three dispersal events of the genus from Europe to East Asia during the early and middle Miocene. Amphicyon sp. from the late Miocene site in the Lower Irrawaddy near Magway, Myanmar, shares the enlarged and anteroposteriorly elongated M2 with Amphicyon zhanxiangi and could be a descendant of the latter species.
