Ben Creisler
Some recent non-dino papers that may be of interest:
====
Stephanie K. Drumheller, James Darlington & Kent A. Vliet (2019)
Surveying death roll behavior across Crocodylia.
Ethology Ecology & Evolution (advance online publication)
The "death roll" is an iconic crocodylian behaviour, and yet it is documented in only a small number of species, all of which exhibit a generalist feeding ecology and skull ecomorphology. This has led to the interpretation that only generalist crocodylians can death roll, a pattern which has been used to inform studies of functional morphology and behaviour in the fossil record, especially regarding slender-snouted crocodylians and other taxa sharing this semi-aquatic ambush predator body plan. In order to test this hypothesis, we surveyed death roll behaviour across animals representing all extant crocodylian species. Animals were prompted to death roll using two methods of stimulation: a feeding cue and an escape cue. The feeding cue involved presenting each animal with a bait item, to which resistance would be applied during a biting event. The second cue involved capturing each animal with a rope or catch pole, a standard technique for capturing crocodylians, but one that also often prompts an attempt to escape. All species tested, except Paleosuchus palpebrosus, exhibited the behaviour in response to at least one of the stimuli. This included the following slender-snouted species: Gavialis gangeticus, Tomistoma schlegelii, Mecistops cataphractus, Mecistops leptorhynchus, Crocodylus johnstoni, and Crocodylus intermedius. The patterns of death roll behavior observed in this survey suggest that this behaviour is not novel to any one crocodylian clade, morphotype, or dietary niche. Also, the prevalence of death rolling behaviour across Crocodylia in response to perceived threats indicates that it is not solely, or maybe even primarily, a feeding behaviour, but is also utilised during inter- and intra-specific conflict as a means to escape or injure an opponent. The results of this case study highlight the importance of using multiple modern analogues when attempting to correlate form and function across diverse clades, both living and extinct.
======
Nicole Klein, Aurore Canoville & Alexandra Houssaye (2019)
Microstructure of vertebrae, ribs, and gastralia of Triassic sauropterygians -- New insights into the microanatomical processes involved in aquatic adaptations of marine reptiles.
The Anatomical Record (advance online publication)
Isolated ribs and vertebrae of Middle Triassic sauropterygians are studied. The vertebrae have a wellâdefined large cavity in their centra, which is a unique feature and is without any modern analogue. The articular facets of vertebrae are made of endochondral bone including calcified as well as uncalcified cartilage. Vertebrae are pachyosteosclerotic in the pachypleurosaurs Neusticosaurus and Serpianosaurus from the Alpine Triassic, and osteosclerotic in the placodont, in the mediumâsized Nothosaurus marchicus, and in the pachypleurosaur Anarosaurus. In large Nothosaurus specimens, the vertebrae are cavernous.
The ribs of all sampled specimens are osteosclerotic, which resembles the microanatomy of long bones in all studied taxa. The proximal to medial part of ribs mainly consist of a compact periosteal cortex surrounding an inner endosteal territory. Towards the distal end of the ribs, the periosteal thickness decreases whereas the endosteal territory increases. Despite a shift from periosteal vs. endosteal tissues, global rib compactness remains relatively constant.
Osteosclerosis in ribs and vertebrae is reached by the same processes as in the long bones: by a relative increase in cortex thickness that is coupled by a reduction of the medullary cavity, by the persistence of calcified cartilage, and by an inhibition of remodelling although some resorption may occur but without complete redeposition of bone. Processes differ from those observed in Permian marine reptiles and some mosasaurines, where either extensive remodelling or inhibition of bone resorption leads to osteosclerosis.
Besides differences regarding the microanatomy, all studied bones of a taxon are consistent in their bone tissue type.
====
Rainer R. Schoch & Max C. Langer (2019)
Interrelationships, palaeobiogeography and early evolution of Stereospondylomorpha (Tetrapoda: Temnospondyli).
Journal of Iberian Geology (advance online publication)
The stereospondylomorph temnospondyls form a diverse group of early tetrapods that survived the Permian-Triassic extinction event and radiated during the Triassic. They encompass Carboniferous and Permian taxa from central and eastern Europe, such as âarchegosauroidsâ, and early-divergent Gondwanan forms, such as rhinesuchids. By the Early Triassic, the group reached a worldwide distribution, with stereospondyls experiencing an impressive diversification and becoming major aquatic predators in fresh water, brackish, and even marine ecosystems. The origin of Stereospondyli dates back into the Permian, but the phylogenetic relationships of stereospondylomorphs, including âarchegosauroidsâ and the first stereospondyls remain unclear, representing the focus of the present study. Incorporating new records of the group to a broad revision of the different phylogenic hypotheses, a 37-taxon sample was scored for 221 morphological characters revised from previous works. The parsimony analysis resulted three most parsimonious trees (MPTs) of 737 steps. Their strict consensus tree depicts Sclerocephalidae and Intasuchidae as early-diverging stereospondylomorphs, âArchegosauroideaâ as paraphyletic array of taxa and Konzhukoviidae as the sister-group of a monophyletic Stereospondyli. An early-diverging and monophyletic Rhinesuchidae is divided into Australerpetinae and Rhinesuchinae, as the sister-group of the clade containing the Permian Peltobatrachus pustulatus, Arachana nigra, and a newly named clade (Superstesâ=ââsurvivorsâ) of Triassic stereospondyls, formed by Lydekkerinidae and Neostereospondyli (Capitosauria and Trematosauria). Likelihood ancestral area reconstructions and time-ranging distributions along phylogeny provided a comprehensive description of early Stereospondylomorpha palaeobiogeography history. The initial evolution of the group took place in Laurasian areas (central and eastern Europe) during the Cisuralian and Guadalupian (early-mid Permian), with a broader Pangaean distribution for Platyoposauridae and Konzhukoviidae. Stereospondyls have Africa as their ancestral area, followed by dispersions to other Gondwanan regions during the Guadalupian and Lopingian (mid-late Permian), revealing a remarkable diversity previous to the P-Tr extinction. In the Triassic, Superstes greatly expanded across the Pangaea, highlighting another significant event in the evolution of Stereospondylomorpha.
====
Hugo Dutel, Manon Galland, Paul Tafforeau, John A. Long, Michael J. Fagan, Philippe Janvier, Anthony Herrel, Mathieu D. Santin, GaÃl ClÃment & Marc Herbin (2019)
Neurocranial development of the coelacanth and the evolution of the sarcopterygian head.
Nature (advance online publication)
The neurocranium of sarcopterygian fishes was originally divided into an anterior (ethmosphenoid) and posterior (otoccipital) portion by an intracranial joint, and underwent major changes in its overall geometry before fusing into a single unit in lungfishes and early tetrapods. Although the pattern of these changes is well-documented, the developmental mechanisms that underpin variation in the form of the neurocranium and its associated soft tissues during the evolution of sarcopterygian fishes remain poorly understood. The coelacanth Latimeria is the only known living vertebrate that retains an intracranial joint. Despite its importance for understanding neurocranial evolution, the development of the neurocranium of this ovoviviparous fish remains unknown. Here we investigate the ontogeny of the neurocranium and brain in Latimeria chalumnae using conventional and synchrotron X-ray micro-computed tomography as well as magnetic resonance imaging, performed on an extensive growth series for this species. We describe the neurocranium at the earliest developmental stage known for Latimeria, as well as the major changes that the neurocranium undergoes during ontogeny. Changes in the neurocranium are associated with an extreme reduction in the relative size of the brain along with an enlargement of the notochord. The development of the notochord appears to have a major effect on the surrounding cranial components, and might underpin the formation of the intracranial joint. Our results shed light on the interplay between the neurocranium and its adjacent soft tissues during development in Latimeria, and provide insights into the developmental mechanisms that are likely to have underpinned the evolution of neurocranial diversity in sarcopterygian fishes.
News:
Fish that outlived dinosaurs reveals secrets of ancient skull evolution
====