PaperPlayer biorxiv paleontology

Link to bioRxiv paper:

http://biorxiv.org/cgi/content/short/2020.08.11.242974v1?rss=1

Authors: Zhu, Y.-a., Giles, S., Young, G., HU, Y., Bazzi, M., Ahlberg, P. E., Zhu, M., Lu, J.

Abstract:

Our understanding of the earliest evolution of jawed vertebrates depends on a credible phylogenetic assessment of the jawed stem gnathostomes collectively known as "placoderms". However, their relationships, and even whether "placoderms" represent a single radiation or a paraphyletic array, remain contentious. Here we describe the endocranial cavity and inner ear of Brindabellaspis stensioi, commonly recovered as a taxon of uncertain affinity branching near the base of "placoderms". While some features of its braincase and endocast resemble those of jawless vertebrates, its inner ear displays a repertoire of crown gnathostome characters. Both parsimony and Bayesian analyses suggest that established hypotheses of "placoderm" relationships are unstable, with newly-revealed anatomy pointing to a potentially radical revision of early gnathostome evolution. Our results call into question the appropriateness of fusiform "placoderms" as models of primitive gnathostome anatomy and raise questions of homology relating to key cranial features.

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Link to bioRxiv paper:

http://biorxiv.org/cgi/content/short/2020.08.10.244210v1?rss=1

Authors: Pei, Y., Duda, J.-P., Reitner, J.

Abstract:

The Permian-Triassic mass extinction included a potentially catastrophic decline of biodiversity, but ecosystem change across this event remains poorly characterized. Here we reconstruct sedimentary factories and ecosystem change across the Permian-Triassic Critical Interval (P-TrCI) in the Xiakou area (South China). Six microfacies (MF) were classified. The succession begins with a eukaryote-controlled carbonate factory (MF-1) that passes upward into an organomineralization-dominated carbonate factory (MF-2-3). Organic-rich marls atop these units reflect carbonate factory collapse (MF-4). Organomineralization-driven carbonate formation restarts prior to the Permian-Triassic boundary (MF-5) and subsequently develops into a mixed carbonate factory where organomineralization and biomineralization are almost equally important (MF-6). MF-1 reflects oxygenated shallow water environments. In contrast, MF-2-6 were all deposited in somewhat deeper environments, some of which episodically exhibited elevated salinities, oxygen depletion, and, possibly, euxinic conditions. Our results demonstrate that distinct changes in carbonate production styles, biodiversity, and environmental conditions are not synchronous at Xiakou. Furthermore, the Xiakou record is strikingly different to that of other localities, even from the same area (e.g., the Global Stratotype Section and Point section at Meishan). Together, these findings highlight the enormous complexity of the P-TrCI and calls simplified views of the Permian-Triassic mass extinction into question.

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Link to bioRxiv paper:

http://biorxiv.org/cgi/content/short/2020.08.10.244061v1?rss=1

Authors: Gagliardi, F., Maridet, O., Becker, D.

Abstract:

The Miocene sands of the Swiss Jura Mountains, long exploited in quarries for the construction industry, have yielded abundant fossil remains of large mammals. Among Deinotheriidae (Proboscidea), two species, Prodeinotherium bavaricum and Deinotherium giganteum, had previously been identified in the Delemont valley, but never described. A third species, Deinotherium levius, from the locality of Charmoille in Ajoie, is reported herein for the first time in Switzerland. These occurrences are dated from the late early to the early late Miocene, correlating to the European Mammal biozones MN4 to MN9. The study is completed by a discussion on the palaeobiogeography of dinotheres at European scale

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Link to bioRxiv paper:

http://biorxiv.org/cgi/content/short/2020.08.09.243048v1?rss=1

Authors: Bolet, A., Stanley, E. L., Daza, J. D., Arias, J. S., Cernansky, A., Vidal-Garcia, M., Bauer, A. M., Bevitt, J. J., Peretti, A., Evans, S. E.

Abstract:

Oculudentavis khaungraae was described based on a tiny skull trapped in amber. The slender tapering rostrum with retracted osseous nares, large eyes, and short vaulted braincase led to its identification as the smallest avian dinosaur on record, comparable to the smallest living hummingbirds. Despite its bird-like appearance, Oculudentavis showed several features inconsistent with its original phylogenetic placement. Here we describe a more complete, specimen that demonstrates Oculudentavis is actually a bizarre lizard of uncertain position. The new interpretation and phylogenetic placement highlights a rare case of convergent evolution rarely seen among reptiles. Our results re-affirm the importance of Myanmar amber in yielding unusual taxa from a forest ecosystem rarely represented in the fossil record.

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Link to bioRxiv paper:

http://biorxiv.org/cgi/content/short/2020.07.23.212324v1?rss=1

Authors: Birarda, G., Cagnato, C., Pantyukhina, I., Stani, C., Cefarin, N., Sorrentino, G., Badetti, E., Marcomini, A., Lubritto, C., Khlopacev, G., Covalenco, S., Obada, T., Skakun, N., Vaccari, L., Longo, L.

Abstract:

Direct evidence for the intentional processing of starch-rich plants during the Paleolithic is scant, and that evidence is often compromised by concerns over preservation and contamination. Our integrated, multimodal approach couples wear-trace analysis with chemical imaging methods to identify the presence of genuine ancient starch candidates (ASC) on ground stones used in the Pontic Steppe starting around 40,000 years ago. Optical and electron microscopy coupled with infrared spectromicroscopy and imaging provide morphological and chemical profiles for ASCs, that partially match the vibrational polysaccharide features of modern reference starches, highlighting diagenetic differences ranging from partial oxidation to mineralization. The results suggest the intentional processing of roots and tubers by means of mechanical tenderization and shed light on the role of dietary carbohydrates during Homo sapiens (HS) colonization of Eurasia, demonstrating a long acquaintance with predictable calorific foods, crucial to maintain homeostasis during the harsh conditions of the Late MIS 3 (40-25 ky).

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Link to bioRxiv paper:

http://biorxiv.org/cgi/content/short/2020.07.08.193839v1?rss=1

Authors: Richard P Dearden, Sam Giles

Abstract:

The teeth of sharks famously form a series of parallel, continuously replacing files borne directly on the mandibular cartilages. In contrast, bony fishes possess site-specific shedding dentition borne on dermal plates. Understanding how these disparate systems evolved is challenging, not least because of poorly understood relationships and the profusion of morphologically and terminologically diverse bones, splints and whorls seen in the earliest chondrichthyans. Here we use tomographic methods to investigate the nature of mandibular structures in several early branching acanthodian-grade stem-chondrichthyans. We characterise the gnathal plates of ischnacanthids as growing bones, and draw similarities between early chondrichthyan and stem gnathostome teeth and jaws. We further build the case for Acanthodopsis, a Carboniferous taxon, as an acanthodid, and show that, unexpectedly, its teeth are borne directly on the mandibular cartilage. Mandibular splints are formed from dermal bone and appear to be an acanthodid synapomorphy. The development of a unidirectionally growing dentition may be a feature of the chondrichthyan total-group. More generally, ischnacanthid and stem gnathostome gnathal plates share a common construction and are likely homologous, and shedding teeth evolved twice in gnathostomes.

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Link to bioRxiv paper:

http://biorxiv.org/cgi/content/short/2020.06.24.168658v1?rss=1

Authors: Rojas, A., Gracia, A., Hernandez-Avila, I., Patarroyo, P., Kowalewski, M.

Abstract:

Despite its importance as the larger component of the modern and Cenozoic brachiopod faunas in the Caribbean region, the ecology and habitat preferences of the terebratulid Tichosina remain poorly understood. We compiled field observations from multiple sites in the Caribbean of Colombia (i.e., San Bernado Bank, Bahia Honda-Guajira, Puerto Escondido, Joint Regime Area Jamaica-Colombia) and data from the R/V Pillsbury program, indicating that Tichosina may have close ecological ties with deep-water corals. In addition, we reviewed literature sources on Cenozoic sediments in the Dominican Republic and found tentative evidence that such ecological ties could have existed since at least the Pliocene. These observations are reminiscent of the Gryphus-anthozoan association observed in the modern Mediterranean continental margin. Understanding to what extent the brachiopod Tichosina is linked to deep-water habitats has implications for the recognition of deep-water macrobenthic communities in the Cenozoic rock record of the Caribbean.

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Link to bioRxiv paper:

http://biorxiv.org/cgi/content/short/2020.06.20.162842v1?rss=1

Authors: Lloyd Evans, D.

Abstract:

Any assessment of whether or not Saccharum species are native or introduced in New Guinea require an evolutionary (in a geological sense), geophysical and climatological assessment of the island. Like many of the land masses circling the Pacific (in the volcanically active region known as the ring of fire) New Guinea is geologically young, with the island in its modern form not pre-dating 2 Ma. Novel modelling of the 74 ka youngest Toba supereruption indicates a potential extinction level tsunami and loss of habitat. The late Pleistocene megafaunal mass extinction and the last glacial maximum (33-16 ka) are two global effects that would have significantly altered the flora on New Guinea; though the implications of these events on New Guinea have not previously been studied. Even if the genus Saccharum was established on the island during pre-historic times the consequences of Toba and other global climate change events means that it would have been eliminated from New Guinea and would have had to be re-introduced during the period of human colonization. Indeed, given the evolution of Saccharums immediate ancestors in Africa and Indochina it is most parsimonious to conclude that it was never native to New Guinea, but was introduced by humans relatively recently.

Little work has been done on palaeotsunami evidence and ancient tsunami modelling in New Guinea. However, the recent recognition that the Aitape skull (dating to about 6 ka) may have been the victim of a tsunami (Goff et al. 2017) show that, in the past, tsunami have pen etrated significantly (about 10 km in this case) into the interior of the island to have a profound effect on biodiversity. This tsunami would have left the north coast of the island impoverished of plant life for several decades after.

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Link to bioRxiv paper:

http://biorxiv.org/cgi/content/short/2020.06.12.147041v1?rss=1

Authors: O'Connor, J., Xing, L., Chiappe, L., Schmitz, L., McKellar, R., Li, G., Yi, Q.

Abstract:

We welcome any new interpretation or alternative hypothesis regarding the taxonomic affinity of the enigmatic Oculudentavis khaungraae. However, here we demonstrate that Li et al. have failed to provide conclusive evidence for the reidentification of HPG-15-3 as a squamate. We analyse this specimen in a matrix that includes a broad sample of diapsid reptiles and resolve support for this identification only when no avian taxa are included. Regardless of whether this peculiar skull belongs to a tiny bird or to a bizarre new group of lizards, the holotype of Oculudentavis khaungraae is a very interesting and unusual specimen, the discovery of which represents an important contribution to palaeontology. Its discovery documents a potential new case of convergent evolution in reptiles, while highlighting the importance of amber deposits for documenting taxa not recorded in sedimentary deposits.

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Link to bioRxiv paper:

http://biorxiv.org/cgi/content/short/2020.06.11.145813v1?rss=1

Authors: Peterman, D. J., Mikami, T., Inoue, S.

Abstract:

Nipponites is a heteromorph ammonoid with a complex and unique morphology that obscures its mode of life and ethology. The seemingly aberrant shell of this Late Cretaceous nostoceratid seems deleterious. However, hydrostatic simulations suggest that this morphology confers several advantages for exploiting a quasi-planktic mode of life. Virtual, 3D models of Nipponites mirabilis were used to compute various hydrostatic properties through 14 ontogenetic stages. At each stage, Nipponites had the capacity for neutral buoyancy and was not restricted to the seafloor. Throughout ontogeny, horizontally facing to upwardly facing soft body orientations were preferred. These orientations were aided by the obliquity of the shells ribs, which were parallel to former positions of the aperture during life. Static orientations were somewhat fixed, inferred by stability values that are slightly higher than extant Nautilus. The initial open-whorled, planispiral phase is well suited to horizontal backwards movement with little rocking. Nipponites then deviates from this coiling pattern with a series of alternating U-shaped bends in the shell. This modification allows for proficient rotation about the vertical axis, while possibly maintaining the option for horizontal backwards movement by redirecting its hyponome. These particular hydrostatic properties likely result in a tradeoff between hydrodynamic streamlining, suggesting that Nipponites assumed a low energy lifestyle of slowly pirouetting in search for planktic prey. Each computed hydrostatic property influences the others in some way, suggesting that Nipponites maintained a delicate hydrostatic balancing act throughout its ontogeny in order to facilitate this mode of life.

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