Dynamic Paleontology

McMenamin, Mark A. S.

doi:10.1007/978-3-319-22777-1

Cited by 12 publications

(13 citation statements)

References 162 publications

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“…The differences between Claudiosaurus and Tupinambis are likely controlled by upregulation in Claudiosaurus of Ptch1 (patched 1) and Hhip1 (hedgehog-interacting protein 1), both of which serve as hedgehog antagonists [26]. The odd variation of vertebral segmental length in Testudo is more likely due to heterotopic distortion of a more conventional tetrapod body plan [27,28].…”

Section: Discussionmentioning

confidence: 99%

Permian Aquatic Reptiles

McMenamin¹

2019

Preprint

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Eight amniote genera (representing four clades) became aquatic during the Permian. The four clades were mesosaurids, tangasaurids, the neodiapsid Claudiosaurus, and the procolophonid Barasaurus. Two of eight genera survived the end-Permian mass extinction, but did not last long into the Mesozoic. A previously undescribed specimen of Claudiosaurus germaini, preserved in a lacustrine concretion from the Sakamena Formation, Madagascar, bears seventeen vertebrae that has been split along an approximate horizontal plane to reveal sections of neural canal casted in white calcite. Enlargement of the neural canal in the sacral region of this specimen of Claudiosaurus (vertebral segments 22-26) is more similar to that of Tupinambis (segments 24-28) than it is to Testudo (segments 16-23). Claudiosaurus skeletal anatomy provides evidence for swim propulsion by both hind limbs and by undulation of a dorsal-ventrally flattened tail. Evidence for the latter includes elongate transverse processes on distal tail vertebrae. Other Permian aquatic reptile genera (Mesosaurus, Hovasaurus, Barasaurus) used snake-like side-to-side tail undulation, whereas Claudiosaurus used cetacean-like up-down tail undulation in the vertical plane. It seems unlikely that any of these animals were particularly fast swimmers.

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Section: Discussionmentioning

confidence: 99%

Permian Aquatic Reptiles

McMenamin¹

2019

Preprint

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“…Several aspects should be mentioned with regard to developmental biology when considering the origin of Chordata and related Cambrian animals. For example, the distinction between the tiny pharyngeal teeth of Haikouella and the larger pharyngeal teeth of Yunnanozoon, homologous features [7] between the two genera, represents the range of variation seen in the early chordate anterior scleritome.…”

Section: Developmental Biology Of Chordate/vetulicolian Originsmentioning

confidence: 99%

Cambrian Chordates and Vetulicolians

McMenamin¹

2019

Geosciences

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Deuterostomes make a sudden appearance in the fossil record during the early Cambrian. Two bilaterian groups, the chordates and the vetulicolians, are of particular interest for understanding early deuterostome evolution, and the main objective of this review is to examine the Cambrian diversity of these two deuterostome groups. The subject is of particular interest because of the link to vertebrates, and because of the enigmatic nature of vetulicolians. Lagerstätten in China and elsewhere have dramatically improved our understanding of the range of variation in these ancient animals. Cephalochordate and vertebrate body plans are well established at least by Cambrian Series 2. Taken together, roughly a dozen chordate genera and fifteen vetulicolian genera document part of the explosive radiation of deuterostomes at the base of the Cambrian. The advent of deuterostomes near the Cambrian boundary involved both a reversal of gut polarity and potentially a two-sided retinoic acid gradient, with a gradient discontinuity at the midpoint of the organism that is reflected in the sharp division of vetulicolians into anterior and posterior sections. A new vetulicolian (Shenzianyuloma yunnanense nov. gen. nov. sp.) with a laterally flattened, polygonal anterior section provides significant new data regarding vetulicolians. Its unsegmented posterior region ('tail') bears a notochord and a gut trace with diverticula, both surrounded by myotome cones.

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“…In many epiphytic symbioses, the benefit to the encrusting epibiont may be restricted just to the provision by the basibiont of a suitable attachment site on the substrate organism. Vinn (2017) reviewed a variety of symbioses between Cambrian macrofossils, including symbioses between frondose algalike organisms and brachiopods (Wang et al 2012) and archaeocyathalgal associations (Rowland & Gangloff 1988, Gandin & Debrenne 2010, McMenamin 2016.…”

Section: Symbiosismentioning

confidence: 99%

An epiphytacean-Girvanella (Cyanobacteria) symbiosis from the Cambrian (Series 3, Drumian) of North Greenland (Laurentia)

Peel¹

2018

Bull. Geosci.

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The widespread Cambrian calcareous cyanobacterium Girvanella is described in symbiotic association with a new epiphytacean, Orpikania freucheni gen. et sp. nov. (Microproblematica), from the Ekspedition Brae Formation (Cambrian Series 3, Drumian Stage) of Freuchen Land, North Greenland. The phosphatized assemblages preserve dendrites of the epiphytacean forming a supporting framework for discrete climbing filaments of Girvanella lianiformis sp. nov. that are firmly attached to their host with holdfasts. Elevation of the slender Girvanella filaments on the framework of the dendrite potentially enhanced their phototactic movement towards the light. Filaments in the cooccurring Girvanella pituutaq sp. nov. are regularly twisted together into a ropelike form which may have assisted elevation above its substrate. •

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Dynamic Paleontology

Abstract: More information about this series at

Cited by 12 publications

References 162 publications

Permian Aquatic Reptiles

Permian Aquatic Reptiles

Cambrian Chordates and Vetulicolians

An epiphytacean-Girvanella (Cyanobacteria) symbiosis from the Cambrian (Series 3, Drumian) of North Greenland (Laurentia)

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