Ben Creisler
Some recent non-dino vertebrate papers:
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http://www.ivpp.ac.cn/cbw/gjzdwxb/pressonline/202103/P020210310559777347580.pdfHere we report a new avian fossil from the Late Miocene Linxia Basin, Northwest China, with exceptional soft-tissue preservation. This specimen preserves parts of cervical vertebrae and tracheal rings that are typically ostrich-like, but cannot be diagnosed at the species level. Therefore, the fossil is referred to Struthio sp. The new specimen was preserved in association with a partial skull of Hipparion platyodus. To explore the soft tissue preservation in a fossil deposited in a terrestrial setting, we applied a combination of analytic methods to investigate the microscopic features of the fossilized avian bone. Bacterial alterations (bone bioerosion) were revealed by light microscopy and petrographic sections under SEM imaging. Soft-tissues (fossilized remnants of endogenous blood vessels and red blood cells) were preserved in one demineralized bone fragment and also observed in the in-situ ground-section. These are the first records of soft-tissue preservation in vertebrate remains from the Late Miocene Linxia Basin. Associated geological and sedimentological evidence combined with our new data provide insights into the postmortem taphonomic conditions of this ostrich specimen. A seasonal monsoon might have facilitated the microbial erosion penecontemporaneous with the burial of the specimen. This study encourages interdisciplinary research involving morphology, sedimentology, geochemistry, and histological soft-tissue analyses to better understand the Late Miocene faunal turnovers, climates, and fossil preservation in the Liushu Formation in northwestern China.Â
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Masaya Iijima, Masanaru Takai, Yuichiro Nishioka, Thaung-Htike, Zin-Maung-Maung-Thein, Naoko Egi, Nao Kusuhashi, Takehisa Tsubamoto, Reiko T. Kono & Ren Hirayama (2021)
Taxonomic overview of Neogene crocodylians in Myanmar.
Vertebrate Paleontology Article: e1879100
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https://doi.org/10.1080/02724634.2021.1879100 https://www.tandfonline.com/doi/full/10.1080/02724634.2021.1879100Although Neogene crocodylians were well documented from Indo-Pakistan, few fossils were known from Southeast Asia, precluding the understanding of their evolutionary and biogeographic history. Here, we describe crocodylians from the Neogene Irrawaddy Formation of central Myanmar and evaluate their taxonomic status. Tebingan, SE of Magway (lower Upper Miocene) yields Gavialis and Crocodylus that differ from the previously known species of each genus, and the Gwebin area, SW of Bagan (Upper Pliocene) produces Crocodylus cf. palaeindicus. Taking into account the materials without provenance data, Neogene crocodylians from Myanmar include at least three gavialids and two Crocodylus that are characterized by different craniomandibular and postcranial features. The body length estimates for the gavialines from Tebingan and an unknown locality in central Myanmar are 7.5 m and 8.6 m, respectively, which exceed the maximum size limit of extant Gavialis gangeticus. Together with the previously reported large taxa, gavialids repeatedly evolved large body sizes in the Neogene of Asia. Gavialis from the Miocene of Myanmar is one of the oldest records of the genus, and its unraised orbital rim suggests that the âtelescopedâ eyes derived later during the genus evolution. Crocodylus cf. palaeindicus from the Pliocene of Myanmar indicates the species range was extended from western India to Myanmar during the Neogene. The absence of Crocodylus siamensis in the Neogene of India and central Myanmar implies the species originated east of central Myanmar.
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Samir ZOUHRI, Philip D. GINGERICH, Bouziane KHALLOUFI, Estelle BOURDON, Sylvain ADNET, StÃphane JOUVE, Najia ELBOUDALI, Ayoub AMANE, Jean-Claude RAGE, Rodolphe TABUCE & France de LAPPARENT de BROIN (2021)
Middle Eocene vertebrate fauna from the Aridal Formation, Sabkha of Gueran, southwestern Morocco.
in STEYER J.-S., AUGÃ M. L. & MÃTAIS G. (eds), Memorial Jean-Claude Rage: A life of paleo-herpetologist. Geodiversitas 43 (5): 121-150
GEODIVERSITAS 43(5): 121-150
doi:
https://doi.org/10.5252/geodiversitas2021v43a5https://sciencepress.mnhn.fr/en/periodiques/geodiversitas/43/5
In the Sahara Desert of southwestern Morocco, the Aridal Formation of Gueran is known for the worldâs richest Bartonian archaic whale assemblage, which includes both protocetids and basilosaurids. Gueran has also yielded another rich and diverse vertebrate fauna described in detail herein âThe chondrichthyan assemblage of twelve species is quite similar to that of the Midawara Formation (Egypt). Actinopterygians include Siluriformes, Percomorpha and rostra of Cylindracanthus Leidy, 1856. Turtles are attributed to at least three indetermined species: two marine cryptodires â a cheloniid and a dermochelyid, and a possible littoral pleurodire, as found in Ad-Dakhla (Morocco) and Fayum (Egypt). The crocodylians comprise at least two longirostrine taxa, including a gavialoid that resembles the late Eocene-early Oligocene Eogavialis africanum Andrews, 1901 from Egypt. The second form is too fragmentary to be identified more precisely than Crocodyliformes indet. Two snake vertebrae belong to Pterosphenus cf. schweinfurthi Andrews, 1901. Two other incomplete snake vertebrae probably belong to Paleophiidae as well. Seabird remains belong to a gigantic soaring pseudo-toothed bird (Pelagornithidae) and constitute the earliest occurrence of the genus Pelagornis sp. Lartet, 1857. This material extends the fossil record of Pelagornis back in time by at least 10 million years. Based on their size and enamel microstructure, mammal dental fragments are attributed to the proboscidean ?Barytherium sp. The Bartonian age of the fauna, initially based on an archaeocete cetacean assemblage, is also supported by chondrichthyans. Affinities of the Gueran faunal assemblage are analyzed in comparison with those from other middle and upper Eocene deposits of North Africa and elsewhere.
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Although currently most taxonomists claim to adhere to the concept of âphylogenetic taxonomyâ, in fact most of the zoological classifications currently published are only in part âphylogeneticâ but include also phenetic or gradist approaches, in their arbitrary choices of the nodes formally recognised as taxa and in their attribution of ranks to these taxa. We here propose a new approach to âphylogenetic taxonomy and nomenclatureâ, exemplified by a phylogenetic classification or cladonomy of the extant amphibians (subclass Lissamphibia of the class Amphibia) derived from a supermatrix-based phylogenetic analysis using 4060 amphibian species, i.e. about half of the 8235 species recognised on 31 October 2020. These taxa were represented by a mean of 3029 bp (range: 197â13849 bp) of DNA sequence data from a mean of 4 genes (range: 1â15). The cladistic tree thus generated was transferred into a classification according to a new taxonomic and nomenclatural methodology presented here, which allows a bijective or isomorphic relationship between the phylogenetic hypothesis and the classification through a rigorous use of suprageneric ranks, in which their hierarchy mirrors the structure of the tree. Our methodology differs from all previous ones in several particulars: [1] whereas the current International Code of Zoological Nomenclature uses only three âgroups of namesâ (species, genus and family), we recognise four nominal-series (species, genus, family and class); [2] we strictly follow the Code for the establishment of the valid nomen (scientific name) of taxa in the three lower nominal-series (however, in a few situations, we suggest improvements to the current Rules of the Code); [3] we provide precise and unambiguous Criteria for the assignment of suprageneric nomina to either the family- or the class-series, excluding nomina proposed expressly under unranked or pseudoranked nomenclatural systems; [4] in the class-series, for which the Code provides only incomplete Rules concerning availability, we provide precise, complete and unambiguous Criteria for the nomenclatural availability, taxonomic allocation and nomenclatural validity and correctness of nomina; [5] we stress the fact that nomenclatural ranks do not have biological definitions or meanings and that they should never be used in an âabsoluteâ way (e.g., to express degrees of genetic or phenetic divergence between taxa or hypothesised ages of cladogeneses) but in a ârelativeâ way: two taxa which are considered phylogenetically as sister-taxa should always be attributed to the same nomenclatural rank, but taxa bearing the same rank in different âcladesâ are by no means âequivalentâ, as the number of ranks depends largely on the number of terminal taxa (species) and on the degree of phylogenetic resolution of the tree; [6] because of this lack of âequivalenceâ, some arbitrary criteria are necessary to fix a starting point for assigning a given suprageneric rank to some taxa, from which the ranks of all other taxa will automatically derive through a simple implementation of the hierarchy of ranks: for this purpose we chose the rank family and we propose a âTen Criteria Procedureâ allowing to fix the position of this rank in any zoological classification. As a result of the implementation of this set of Criteria, we obtained a new ranked classification of extant lissamphibians using 25 suprageneric ranks below the rank class (11 class-series and 14 family-series ranks), and including 34 class-series and 573 family-series taxa, and where the 575 genera we recognise are referred to 69 families and 87 subfamilies. We provide new nomina and diagnoses for 10 class-series taxa, 171 family-series taxa, 14 genus-series taxa and 1 species. As many new species of amphibians are permanently described, this classification and its nomenclature will certainly have to change many times in the future but, using the clear, explicit, complete, automatic and unambiguous methodology presented here, these changes will be easy to implement, and will not depend on subjective and arbitrary choices as it has too often been the case in the last decades. We suggest that applying this methodology in other zoological groups would improve considerably the homogeneity, clarity and usefulness of zoological taxonomy and nomenclature.
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Fish evolution papers:
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The postcranial axial skeleton of actinopterygian fishes is typically divided into three regions: (1) an anterior abdominal region, (2) a posterior caudal region and (3) those vertebrae supporting the caudal fin. However, in some actinopterygians, the axial skeleton is more finely subdivided, with up to six morphologically distinct subâregions recognized. Phylogenetic continuity and homology of structures across these subâregions have not been investigated in detail, either between or among groups. We examine variation in axial regionalization in saurichthyid fishes, a clade of extinct nonâteleostean actinopterygians with highly variable axial skeletal morphology but an otherwise conservative body plan, and compare these findings to other nonâteleostean actinopterygians to assess conservation of a regionalized axial skeleton within bony fishes. We document up to eight distinct regions in the vertebral column of Triassic Saurichthys: (1) a postoccipital region, (2) an anterior and (3) a posterior abdominal region, (4) a transitional region spanning the abdominalâcaudal boundary, (5) an anterior and (6) a posterior caudal region and (7) preural and (8) ural regions. Based on taphonomical and morphological evidence, the transitional region appears to function in axial stiffening in the area of the median fins, whereas the abdominal region is highly flexible. The degree to which these axial regions are osteologically differentiated is highly variable across Saurichthyidae, implying iterative evolution of differentiation and deâdifferentiation over relatively short geological timescales. Such variably expressed regionalization was also identified in the outgroup nonâteleostean actinopterygians Birgeria and Australosomus. Despite variation in morphological disparity, the regions identified in saurichthyids correlate well with those documented in some teleosts and Paleozoic actinopterygians, suggesting potential deep patterning homology but independent evolution of specific regionalized axial morphologies in response to changing functional demands.
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Actinopterygians (ray-finned fishes) are the most diverse group of living fishes, but have a sparse Devonian fossil record restricted to low palaeolatitudes. Here we report a new actinopterygian from the Paranà Basin of Brazil, which occupied a circumpolar position in the Palaeozoic. Available geological evidence supports a Middle Devonian or older age for this taxon, which shares features of the mandibular symphysis with the latest Devonian Tegeolepis. A phylogenetic analysis resolves these two as sister taxa. This new record expands the palaeogeographic distribution of Devonian ray-fins and suggests that gaps in their fossil record might be filled by exploring poorly sampled high-latitude localities within the Malvinokaffric Realm.
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Luca Jaselli & Christopher J. Duffin (2021)
New data on the Early Jurassic biodiversity of the Lombardy Basin (Southern Alps, Italy) and the earliest record Sphenodus (Chondrichthyes, Neoselachii).
Rivista Italiana di Paleontologia e Stratigrafia 127(1): 163-177.
DOI:
https://doi.org/10.13130/2039-4942/15225https://riviste.unimi.it/index.php/RIPS/article/view/15225Free pdf:
https://riviste.unimi.it/index.php/RIPS/article/view/15225/14038At the beginning of the Jurassic, the initial stages of the rifting that preceded the opening of the Alpine Tethys led to the establishment of the Lombardy basin, characterized by a shallow water marine palaeoenvi-ronment inhabited by highly diversified ecological communities. Macrofossil records from the whole Lower Jurassic succession of Lombardy are currently mostly confined to invertebrates. The earliest occurrence of marine vertebrates is from the Sinemurian Moltrasio Limestone of Osteno (Varese), subsequent to the Triassic/Jurassic boundary (TJB) post-crisis recovery.
Here, we describe material from the Roncola section (Roncola San Bernardo, Bergamo) of the Sedrina Li-mestone (upper Hettangian), consisting of a dense accumulation of crinoid skeletal remains belonging to Balanocrinus ticinensis Hess, 2006. Among them are three isolated neoselachian teeth assigned to the genus Sphenodus Agassiz, 1843.
This new discovery is significant and extends our knowledge of the biodiversity of the Lombardy basin Jurassic, mainly because these dental remains represent the earliest vertebrate macrofossils ever documented from this area after the Triassic/Jurassic boundary. Sphenodus (which ranges from the Sinemurian to the Danian) is a fairly ubiquitous Sinemurian neoselachian shark but this new record moves its First Appearance Datum (FAD) back to the Hettangian stage.
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Victor J. Perez, Ronny M. Leder, and Teddy Badaut (2021)
Body length estimation of Neogene macrophagous lamniform sharks (Carcharodon and Otodus) derived from associated fossil dentitions.
Palaeontologia Electronica, 24(1): a09.
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https://doi.org/10.26879/1140https://palaeo-electronica.org/content/2021/3284-estimating-lamniform-body-sizeThe megatooth shark, Otodus megalodon, is widely accepted as the largest macrophagous shark that ever lived; and yet, despite over a century of research, its size is still debated. The great white shark, Carcharodon carcharias, is regarded as the best living ecological analog to the extinct megatooth shark and has been the basis for all body length estimates to date. The most widely accepted and applied method for estimating body size of O. megalodon was based upon a linear relationship between tooth crown height and total body length in C. carcharias. However, when applying this method to an associated dentition of O. megalodon (UF-VP-311000), the estimates for this single individual ranged from 11.4 to 41.1 m. These widely variable estimates showed a distinct pattern, in which anterior teeth resulted in lower estimates than posterior teeth. Consequently, previous paleoecological analyses based on body size estimates of O. megalodon may be subject to misinterpretation. Herein, we describe a novel method based on the summed crown width of associated fossil dentitions, which mitigates the variability associated with different tooth positions. The method assumes direct proportionality between the ratio of summed crown width to body length in ecologically and taxonomically related fossil and modern species. Total body lengths were estimated from 11 individuals, representing five lamniform species: Otodus megalodon, Otodus chubutensis, Carcharodon carcharias, Carcharodon hubbelli, and Carcharodon hastalis. The method was extrapolated for the largest known isolated upper tooth of O. megalodon, resulting in a maximum body length estimate of 20 m.
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Tetsuto Miyashita, Robert W. Gess, Kristen Tietjen & Michael I. Coates (2021)
Non-ammocoete larvae of Palaeozoic stem lampreys
Nature (advance online publication)
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https://doi.org/10.1038/s41586-021-03305-9https://www.nature.com/articles/s41586-021-03305-9 Ammocoetesâthe filter-feeding larvae of modern lampreysâhave long influenced hypotheses of vertebrate ancestry. The life history of modern lampreys, which develop from a superficially amphioxus-like ammocoete to a specialized predatory adult, appears to recapitulate widely accepted scenarios of vertebrate origin. However, no direct evidence has validated the evolutionary antiquity of ammocoetes, and their status as models of primitive vertebrate anatomy is uncertain. Here we report larval and juvenile forms of four stem lampreys from the Palaeozoic era (Hardistiella, Mayomyzon, Pipiscius, and Priscomyzon), including a hatchling-to-adult growth series of the genus Priscomyzon from Late Devonian Gondwana. Larvae of all four genera lack the defining traits of ammocoetes. They instead display features that are otherwise unique to adult modern lampreys, including prominent eyes, a cusped feeding apparatus, and posteriorly united branchial baskets. Notably, phylogenetic analyses find that these non-ammocoete larvae occur in at least three independent lineages of stem lamprey. This distribution strongly implies that ammocoetes are specializations of modern-lamprey life history rather than relics of vertebrate ancestry. These phylogenetic insights also suggest that the last common ancestor of hagfishes and lampreys was a macrophagous predator that did not have a filter-feeding larval phase. Thus, the armoured 'ostracoderms' that populate the cyclostome and gnathostome stems might serve as better proxies than living cyclostomes for the last common ancestor of all living vertebrates.
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Long-accepted theory of vertebrate origin upended by fossilized fish larvae
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The hypothesis of the Great Evolutionary Faunas is a foundational concept of macroevolutionary research postulating that three global mega-assemblages have dominated Phanerozoic oceans following abrupt biotic transitions. Empirical estimates of this large-scale pattern depend on several methodological decisions and are based on approaches unable to capture multiscale dynamics of the underlying Earth-Life System. Combining a multilayer network representation of fossil data with a multilevel clustering that eliminates the subjectivity inherent to distance-based approaches, we demonstrate that Phanerozoic oceans sequentially harbored four global benthic mega-assemblages. Shifts in dominance patterns among these global marine mega-assemblages were abrupt (end-Cambrian 494 Ma; end-Permian 252 Ma) or protracted (mid-Cretaceous 129 Ma), and represent the three major biotic transitions in Earthâs history. Our findings suggest that gradual ecological changes associated with the Mesozoic Marine Revolution triggered a protracted biotic transition comparable in magnitude to the end-Permian transition initiated by the most severe biotic crisis of the past 500 million years. Overall, our study supports the notion that both long-term ecological changes and major geological events have played crucial roles in shaping the mega-assemblages that dominated Phanerozoic oceans.
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