Ben Creisler
Some recent non-dino papers:
New faunal information from the south area of Laramidia is presented.
Mexico has the southernmost Upper Cretaceous localities of turtles for North America.
New occurrences of turtles are reported from The Aguja Formation.
The new specimens add to the diversity of the Late Cretaceous of Mexico.
Abstract
Fragments of turtle shell are known from several Upper Cretaceous formations in Mexico, including Corral de Enmedio and Packard Shale, Sonora; Aguja and Cerro del Pueblo, Coahuila; San Carlos, Chihuahua; El Gallo, Baja California; and Ocozocoautla, Chiapas. Turtles are important members of Upper Cretaceous vertebrate assemblages throughout North America and are considered a useful tool to define biogeographic patterns. The Upper Cretaceous sedimentary rocks exposed in the Aguja Formation record the final transgressive/regressive sequence of the Western Interior Cretaceous Seaway and the subsequent transition from a marine to terrestrial environment. The total area of outcrops is small compared to correlative exposures of these strata elsewhere in North America, in spite of this, numerous invertebrate and vertebrate fossils have been collected. The Aguja Formation in Texas preserves one of the southernmost well-studied Upper Cretaceous (Campanian) terrestrial vertebrate faunas in North America; contrary to what happens with the outcrops in northern Chihuahua, where the record of terrestrial vertebrates is scarce and especially those related to Testudines. Non-marine strata of the Aguja Formation do not appear to be present farther south in Mexico, and this is the reason why the Aguja fauna is relevant to documenting latitudinal variation in Campanian continental faunal associations. In this paper, the richness of Upper Cretaceous turtles collected from three localities within the Aguja Formation in Chihuahua is reviewed. Six taxa are recognized based on shell fragments with distinctive sculpture patterns: stem cryptodires, including cf. Baenidae, c.f. Denazinemys nodosa and cf. Compsemys victa, and crown group cryptodires including trionychians (trionchids and Basilemys sp.) and a kinosternoid (cf. Yelmochelys rosarioae). With the recognition of these taxa, new records are reported for the Aguja Formation (e.g. cf. Yelmochelys rosarioae) and Mexico (e.g. c.f. Denazinemys nodosa). The knowledge of Cretaceous turtle richness of the Aguja Formation and Mexico is increased and confirms the proposal of the variability richness along the North American localities. This latitudinal variability suggests that at any time turtles would have had a climatically controlled northern limit of distribution, and the richness of turtles would have decreased as this limit was reached.
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Epileolis reshetovi gen. et sp. nov.Â
V. R. Alifanov (2020)
A new lizard (Agamidae, Iguania) from the Late Paleocene of southern Mongolia.
Paleontological Journal 54(4): 89-92 (Russian edition)
DOI: 10.31857/S0031031X20040030
https://www.elibrary.ru/item.asp?id=42890268
A lizard Epileolis reshetovi gen. et sp. nov., Agamidae, is described from the late Paleocene of South Mongolia. A new form is established on a find of the left dentary with teeth. The new taxon has a narrow base of the prenatal teeth, seven canine-like teeth and a large coronoid process of the dentary.
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Benthosuchus lukyanovi sp. nov.Â
B. I. Morkovin (2020)
New benthosuchid (Amphibia: Temnospondyli) from the Lower Triassic of the Moscow Syncline.
Paleontological Journal 54(4): 79-88 (Russian edition)
DOI: Â10.31857 / S0031031X20040182
https://www.elibrary.ru/item.asp?id=42890267
A new benthosuchid Benthosuchus lukyanovi sp. nov. is described from the Early Triassic deposits of Bludnovo location in Vologda Region. The new species have the largest skull in comparison to the previously known Benthosuchus individuals. Morphological differences between B. lukaynovi and other representatives of the genus were noticed. A significant part of them resemble characteristic features of the trematosauroid structure plan, as: close position of the supraorbital canals (sulci supraorbitales) to the sagittal suture in the internarial space, weakly bend angular of the lower jaw, and strongly elongated posterior Meckelian foramen. Obtained data expand our understanding of the morphological evolution of benthosuchids during the early stages of the trematosaurid plan organization.
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Free pdf:
Kellen M Verissimo, Louise N Perez, Aline C Dragalzew, Gayani Senevirathne, Sylvain Darnet, Wainna RB Mendes, Ciro AS Neves, Erika M dos Santos, Cassia NS Moraes, Ahmed Elewa, Neil H Shubin, Nadia B Froebisch, Josane F Sousa & Igor Schneider (2020)
Salamander-like tail regeneration in the West African lungfish.
bioRxiv 2020.02.12.946319 (preprint)
doi:
https://doi.org/10.1101/2020.02.12.946319https://www.biorxiv.org/content/10.1101/2020.02.12.946319v2
Salamanders, frog tadpoles, and diverse lizards have the remarkable ability to regenerate tails. Paleontological data suggests that this capacity is plesiomorphic, yet when the developmental and genetic architecture of tail regeneration arose is poorly understood. Here we show morphological and molecular hallmarks of tetrapod tail regeneration in the West African lungfish Protopterus annectens, a living representative of the sister group of tetrapods. As in salamanders, lungfish tail regeneration occurs via formation of a proliferative blastema and restores original structures, including muscle, skeleton and spinal cord. In contrast to lizards and similar to salamanders and frogs, lungfish regenerate spinal cord neurons and reconstitute dorsoventral patterning of the tail. Similar to salamander and frog tadpoles, Shh is required for lungfish tail regeneration. Through RNA-seq analysis of uninjured and regenerating tail blastema, we show that the genetic program deployed during lungfish tail regeneration maintains extensive overlap with that of tetrapods, with the upregulation of genes and signaling pathways previously implicated in amphibian and lizard tail regeneration. Furthermore, the lungfish tail blastema showed marked upregulation of genes encoding post-transcriptional RNA processing components and transposon-derived genes. Our results show that developmental processes and genetic program of tetrapod tail regeneration were present at least near the base of the sarcopterygian clade and establish the lungfish as a valuable research system for regenerative biology.
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Free pdf:
Trina Y. Du & Emily M. Standen (2020)
Terrestrial acclimation and exercise lead to bone functional response in Polypterus senegalus pectoral fins.
Journal of Experimental Biology 2020 223: jeb217554
doi: 10.1242/jeb.217554
https://jeb.biologists.org/content/223/11/jeb217554Free pdf:
https://jeb.biologists.org/content/jexbio/223/11/jeb217554.full.pdfThe ability of bones to sense and respond to mechanical loading is a central feature of vertebrate skeletons. However, the functional demands imposed on terrestrial and aquatic animals differ vastly. The pectoral girdle of the basal actinopterygian fish Polypterus senegalus was previously shown to exhibit plasticity following terrestrial acclimation, but the pectoral fin itself has yet to be examined. We investigated skeletal plasticity in the pectoral fins of P. senegalus after exposure to terrestrial loading. Juvenile fish were divided into three groups: a control group was kept under aquatic conditions without intervention, an exercised group was also kept in water but received daily exercise on land, and a terrestrial group was kept in a chronic semi-terrestrial condition. After 5 weeks, the pectoral fins were cleared and stained with Alcian Blue and Alizarin Red to visualize cartilage and bone, allowing measurements of bone length, bone width, ossification and curvature to be taken for the endochondral radial bones. Polypterus senegalus fin bones responded most strongly to chronic loading in the terrestrial condition. Fish that were reared in a terrestrial environment had significantly longer bones compared with those of aquatic controls, wider propterygia and metapterygia, and more ossified metapterygia and medial radials, and they showed changes in propterygial curvature. Exercised fish also had longer and more ossified medial radials compared with those of controls. Polypterus senegalus fin bones exhibit plasticity in response to novel terrestrial loading. Such plasticity could be relevant for transitions between water and land on evolutionary scales, but key differences between fish and tetrapod bone make direct comparisons challenging.
Commentary:
Dinosaur eels build up their fin bones for life on land