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[dinosaur] Paleognath gigantism + Palaeopython helveticus + Rubrognathus, new tetrapodomorph




Ben Creisler
bcreisler@gmail.com


Some recent non-dino papers not yet mentioned:


Nicholas M.A. Crouch & Julia A. Clarke (2019)
Body size evolution in palaeognath birds is consistent with Neogene cooling-linked gigantism.
Palaeogeography, Palaeoclimatology, Palaeoecology (advance online publication)
doi: https://doi.org/10.1016/j.palaeo.2019.05.046
https://www.sciencedirect.com/science/article/pii/S0031018219301877

Highlights

Strong trend for shifts in size co-occurring with changes in global climate
Heaviest taxa, those exceeding 120âkg, found only in last 9 million years
Island-dwelling and continental taxa show similar pattern
Result robust against the use of different predictive equations


Abstract

Palaeognathae is an extant clade of birds with body masses ranging over several orders of magnitude of kilograms, including the largest-yet described terrestrial avian species. Most studies have suggested flight loss and increasing body size began early in its evolutionary history, prior to the divergence of the major extant lineages. However, recent phylogenetic work suggests body size increases occurred more recently and independently within many extant lineages. Here, we use linear regression equations to estimate the masses of extinct taxa from both the crown and stem of Palaeognathae to test these hypotheses. We allocate fragmentary specimens to discrete body mass categories to accommodate additional species for which more precise body mass estimation is not possible. The first fossil evidence for an increase in maximum palaeognath body size, from approximately that of a rhea (20âkg) or smaller to ostrich size (100âkg), is Miocene in age (approximately 20âMa). The heaviest taxa, those exceeding 120âkg, all occur within the last 9 million years. Molecular divergence dating estimates for the crown ages of palaeognath subclades pre-date the oldest preserved material, often significantly; however, plotting the lightest member of each clade at the estimated crown ages does not change the observed pattern. These results may be affected by the predictive model used to estimate the mass of extinct taxa, but the observed trends in body mass do not change when four models from different studies are used. Both island-dwelling and continental clades show broad temporal congruence in the timing of their estimated gain of large body sizes, meaning geographical restriction on islands does not alone explain the observed trend. We suggest large and giant Palaeognathae body sizes may be more closely linked to global cooling which creates selective pressures on body size for thermoregulation, as well as causing landscape changes which alters dietary and locomotory requirements. Global cooling has received extensive attention as a driver of mammalian body size extremes but has been relatively little discussed with respect to birds.

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Loredana Macaluso, Jeremy E. Martin, Letizia Del Favero & Massimo Delfino (2019)
Revision of the crocodilians from the Oligocene of Monteviale, Italy, and the diversity of European eusuchians across the Eocene-Oligocene boundary
Journal of Vertebrate Paleontology Article: e1601098
doi: Âhttps://doi.org/10.1080/02724634.2019.1601098 Â
https://www.tandfonline.com/doi/full/10.1080/02724634.2019.1601098


Crocodilian remains from the Oligocene fossil locality of Monteviale, northeastern Italy, have historically been referred to different genera, but all material was recently assigned to Diplocynodon cf. D. ratelii Pomel, 1847. The purpose of the present work is to clarify the systematics of the known crocodilian remains from Monteviale. The largest collection is housed in Padua, Italy, but museums in La Rochelle, France; Basel, Switzerland; and London, United Kingdom reposit crocodilian remains of uncertain provenance but which are clearly from either Monte Bolca or Monteviale. Radiogenic strontium isotope ratios were measured on the embedding lignite of those specimens to investigate their provenance. The material belongs to the genus Diplocynodon, but it clearly differs from D. ratelii because the nasal elements are excluded from the external nares. Diplocynodon from Monteviale shares the same general suture pattern of the skull with the two species D. tormis and D. muelleri. Diplocynodon muelleri and specimens from Monteviale are also congruent in terms of shape and proportion of the supratemporal fenestrae. However, a revision of D. muelleri is currently needed; thus, the Monteviale species is identified as Diplocynodon cf. D. muelleri. In order to examine the relationships of Diplocynodon from Monteviale, a phylogenetic analysis was carried out and points to a particularly close relationship among D. muelleri, D. tormis, and the Diplocynodon from Monteviale. The occurrence of Asiatosuchus in Monteviale is rejected, supporting the hypothesis of a reduction in crocodilian diversity around the Eocene-Oligocene boundary in Europe.


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Palaeopython helveticus sp. nov.

Georgios L. Georgalis & Torsten M. Scheyer (2019)
A new species of Palaeopython (Serpentes) and other extinct squamates from the Eocene of Dielsdorf (Zurich, Switzerland).
Swiss Journal of Geosciences (advance online publication)
DOI: https://doi.org/10.1007/s00015-019-00341-6
https://link.springer.com/article/10.1007/s00015-019-00341-6


The lizard and snake fauna from the late middleâlate Eocene (MP 16âMP 20) of Dielsdorf, near Zurich, Switzerland, is described comprehensively in this paper. Detailed comparisons of the Dielsdorf material with other extinct taxa allow us to establish a new species of the large "booid" genus Palaeopython, i.e., Palaeopython helveticus sp. nov., characterized by a unique combination of vertebral features, most prominently a highly vaulted neural arch. Other squamates of the Dielsdorf assemblage comprise the large lizard Palaeovaranus sp. and as many as three other taxa of snakes, i.e., Palaeopython cf. fischeri, Palaeopython sp. (morphotype 3), and "Booidea" indet. We conducted micro-CT scanning in the Palaeovaranus dentary, which confirmed the presence of plicidentine in this lizard genus. Micro-CT scanning was also conducted in differently sized snake vertebrae from our sample, revealing that the respective anatomical differences were probably due to ontogenetic variation. This is the first time that micro-CT scanning is applied in Palaeovaranus and Palaeopython. The importance of this method for potentially clarifying the taxonomy and precise affinities of extinct snakes is addressed. We also provide digital 3D model reconstructions of the Palaeovaranus dentary and Palaeopython vertebrae (including that of the holotype of Palaeopython helveticus sp. nov.) for the first time. The palaeobiogeographic significance of the Dielsdorf lizards and snakes is discussed and the sympatric occurrences of the genera Palaeovaranus and Palaeopython throughout the Eocene of Europe are presented in detail.

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Rubrognathus kuleshovi n. gen. et sp.ÂÂ

Oleg A. LEBEDEV Âand GaÃl CLÃMENT (2019)
New tetrapodomorph vertebrates from the Yam-Tesovo locality (Amata Regional Stage, MiddleâUpper Devonian) of Leningrad Region, northwestern Russia.
Earth and Environmental Science Transactions of The Royal Society of Edinburgh 109(1-2): 61-73
[Special Issue: Fossils, Function and Phylogeny: Papers on Early Vertebrate Evolution in Honour of Professor Jennifer A. Clack]
doi: https://doi.org/10.1017/S1755691018000907
https://www.cambridge.org/core/journals/earth-and-environmental-science-transactions-of-royal-society-of-edinburgh/article/new-tetrapodomorph-vertebrates-from-the-yamtesovo-locality-amata-regional-stage-middleupper-devonian-of-leningrad-region-northwestern-russia/19FD34EB7FDEC2DA80AD8CFB0FE7097B


Each piece of data is valuable for unearthing the earliest history of tetrapod origin. Despite frequently incomplete preservation, each skeletal element provides important information on the morphology, phylogeny and faunistic diversity of early tetrapodomorphs. We describe here new and earlier collected material from the fossil vertebrate site Yam-Tesovo on the Oredezh River (Leningrad Region, northwestern Russia) in the deposits of the Yam-Tesovo Formation within the Amata Regional Stage (?lowermost Frasnian, Upper Devonian). Upon similarity of their dermal ornamentation, two mandibular fragments are suggested to belong to the new tetrapodomorph taxon Rubrognathus kuleshovi n. gen. et sp. This species demonstrates a general 'elpistostegalian' morphological pattern with some early tetrapod characters. The new taxon is characterised by an almost closed intercoronoid fossa, a prearticular that is strongly convex in section and bearing small teeth along its dorsal margin, low vertical coronoid laminae and coronoid fangs that enter the coronoid tooth row. The mandibular canal runs partly in open groove or opens to the surface by a row of large pores. The dermal ornament consists of a network of small ridges forming tubercles in the nodes. The postfrontal assigned to Tetrapodomorpha shows a 'tetrapod-like' pits-and-ridges sculpturing and a supraorbital ridge characteristic of early tetrapods as well as 'elpistostegalians'. Its long posterolateral bone margin demonstrates a lateral projection similar to that in Tiktaalik and unknown in other âelpistostegalians' and early tetrapods. An unusually flattened vomer is doubtfully related to the tetrapodomorph genus Livoniana Ahlberg, LukÅeviÄs & Mark-Kurik, 2000, based upon characteristic multiple tooth rows. Teeth in rows decrease labially and show no clearly enlarged fang pairs. New finds of the last two decades present the earliest records of some tetrapod characters in non-limbed tetrapodomorphs. This challenges previous hypotheses on the origin of tetrapods.


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