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[dinosaur] Neurocentral suture closure in rhynchosaurs + fish-tetrapod brain transition + fossil melanosomes + more,




Ben Creisler
bcreisler@gmail.com

Some recent non-dino papers:


Clara Heinrich, Voltaire D. Paes Neto, Marcel B. Lacerda, AgustÃn G. Martinelli, Maico S. Fiedler & ÂCesar L. Schultz (2021)
The ontogenetic pattern of neurocentral suture closure in the axial skeleton of Hyperodapedontinae (Archosauromorpha, Rhynchosauria) and its evolutionary implications.
Palaeontology (advance online publication)
doi: https://doi.org/10.1111/pala.12528
https://onlinelibrary.wiley.com/doi/10.1111/pala.12528


DATA ARCHIVING STATEMENT:
Data for this study, including supplementary information and tables, are available in the Dryad Digital Repository: https://doi.org/10.5061/dryad.zcrjdfn9c


Understanding the ontogeny of a taxon is a crucial step to properly elucidate its taxonomy and evolution. However, aside from histological data, osteological criteria for assessing maturity are considered lineage specific or controversial. The sequence of neurocentral suture closure of the axial skeleton of extant crocodilians, which occurs in a posteriorâanterior sequence, is a nonâdestructive method used to determine maturity in extinct reptiles. However, its use in extinct archosaurs not closely related to crocodilians is debatable, as the ancestral condition of Archosauria is unknown and variation occurs in timing and sequence orientation within the clade. We have assessed the pattern of neurocentral suture closure of Hyperodapedontinae rhynchosaurs, an early archosauromorph clade distantly related to archosaurs. Unlike extant crocodilians, they exhibit an anteriorâposterior sequence neurocentral suture closure. Relative size and other ontogenetic markers suggest that neurocentral closure in the Hyperodapedontinae correlates with aging, although closed sutures were rare in the sample. A high number of open or partially open sutures in mature individuals indicate that they remained open during most of their life. Our study indicates that: (1) the delayed neurocentral closure may be a paedomorphic heterochronic process in Hyperodapedontinae, as it contrasts with the fully closed neurocentral sutures of early diverging nonâhyperodapedontine rhynchosaurs; (2) the assumption that open neurocentral sutures indicates immaturity in extinct reptiles is not always correct; and (3) the delayed closure may have originated independently in several archosauromorph lineages, but the ancestral condition of Archosauria probably follows the crocodilian closure pattern.


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Free pdf:

Alice M. Clement, Corinne L. Mensforth, T. J. Challands, Shaun P. Collin and John A. Long (2021)
Brain Reconstruction Across the Fish-Tetrapod Transition; Insights From Modern Amphibians.
Frontiers in Ecology and Evolution 9:640345
doi: https://doi.org/10.3389/fevo.2021.640345
https://www.frontiersin.org/articles/10.3389/fevo.2021.640345/full



The fish-tetrapod transition (which incorporates the related fin-limb and water-land transitions) is celebrated as one of the most important junctions in vertebrate evolution. Sarcopterygian fishes (the "lobe-fins") are today represented by lungfishes and coelacanths, but during the Paleozoic they were much more diverse. It was some of these sarcopterygians, a lineage of the tetrapodomorph fishes, that gave rise to tetrapods (terrestrial vertebrates with limbs bearing digits). This spectacular leap took place during the Devonian Period. Due to the nature of preservation, it is the hard parts of an animalâs body that are most likely to fossilize, while soft tissues such as muscular and brain tissues, typically fail to do so. Thus, our understanding of the adaptations of the hard skeletal structures of vertebrates is considerably greater than that of the soft tissue systems. Fortunately, the braincases of early vertebrates are often ossified and thereby have the potential to provide detailed morphological information. However, the correspondence between brain and endocast (an internal mold of the cavity) has historically been considered poor in most "lower" vertebrates and consequently neglected in such studies of brain evolution. Despite this, recent work documenting the spatial relationship in extant basal sarcopterygians (coelacanth, lungfish, axolotl, and salamander) has highlighted that this is not uniformly the case. Herein, we quantify and illustrate the brain-endocast relationship in four additional extant basal tetrapod exemplars: neobatrachian anurans (frogs) Breviceps poweri and Ceratophrys ornata; and gymnophionans (caecilians) Gegeneophis ramaswamii and Rhinatrema bivittatum. We show that anurans and caecilians appear to have brains that fill their endocasts to a similar degree to that of lungfishes and salamanders, but not coelacanth. Ceratophrys has considerably lower correspondence between the brain and endocast in the olfactory tract and mesencephalic regions, while Breviceps has low correspondence along its ventral endocranial margin. The brains of caecilians reflect their endocasts most closely (vol. ~70%). The telencephalon is tightly fitted within the endocast in all four taxa. Our findings highlight the need to adequately assess the brain-endocast relationship in a broad range of vertebrates, in order to inform neural reconstructions of fossil taxa using the Extant Phylogenetic Bracket approach and future studies of brain evolution.

**
News:

When our evolutionary ancestors first crawled onto land, their brains only half-filled their skulls

https://sciencex.com/news/2021-03-evolutionary-ancestors-brains-half-filled-skulls.html

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Free pdf:

Valentina Rossi, Samuel M. Webb & Maria McNamara (2021)
Maturation experiments reveal bias in the chemistry of fossil melanosomes.
Geology (advance online publication)
doi: https://doi.org/10.1130/G48696.1
https://pubs.geoscienceworld.org/gsa/geology/article/doi/10.1130/G48696.1/595631/Maturation-experiments-reveal-bias-in-the


Fossil melanosomes are a major focus of paleobiological research because they can inform on the original coloration, phylogenetic affinities, and internal anatomy of ancient animals. Recent studies of vertebrate melanosomes revealed tissue-specific trends in melanosome-metal associations that can persist in fossils. In some fossil vertebrates, however, melanosomes from all body regions are enriched only in Cu, suggesting diagenetic overprinting of original chemistry. We tested this hypothesis using laboratory experiments on melanosomes from skin and liver of the African clawed frog Xenopus laevis. After maturation in Cu-rich media, the metal chemistry of melanosomes from these tissues converged toward a common composition, and original differences in Cu oxidation state were lost. Elevated Cu concentrations and a pervasive Cu(II) signal are likely indicators of diagenetically altered melanosomes. These results provide a robust experimental basis for interpretating the chemistry of fossil melanosomes.


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Scott Jarvie, Trevor H. Worthy, FrÃdÃrik SaltrÃ, R. Paul Scofield, Philip J. Seddon & Alison Cree (2021)
Using Holocene fossils to model the future: Distribution of climate suitability for tuatara, the last rhynchocephalian.
Journal of Biogeography (advance online publication)
doi: https://doi.org/10.1111/jbi.14092
https://onlinelibrary.wiley.com/doi/10.1111/jbi.14092


Aim

Correlative species distribution models (SDMs) are typically trained using only the contemporary distribution of species; however, recent records might reflect an incomplete description of a species' niche, limiting the reliability of predictions. SDMs linking fossil records have the potential to improve conservation decisions under humanâinduced climate change. Here, we built SDMs using presence records from contemporary and Holocene records to enable estimations of climatically suitable area under current and future climate scenarios.

Location

Aotearoa New Zealand

Taxon

Tuatara, Sphenodon punctatus

Methods

For an evolutionary relict found in Aotearoa New Zealand, the tuatara (Sphenodon punctatus), we built SDMs using presence records from contemporary and Holocene records to estimate climatically suitable area under current and future climate scenarios. We also use our detailed knowledge of the Holocene distribution and remnant populations to examine niche shifts following the arrival of humans and associated introduction of mammalian predators. To build SDMs, we use presence records from four sources: (a) remnant populations, (b) radiocarbonâdated fossil deposits from the Holocene, (c) other fossil deposits containing tuatara bones of Holocene age and iv) islands from which tuatara are known or highly likely to have become extinct.

Results

We found shifts in the niche of tuatara due to niche unfilling. Incorporating locations of Holocene deposits and/or all past locations in SDMs led to larger areas of climatically suitable area being identified compared to SDMs derived from remnant populations only. Using all presence records, under climate change projections for 2090, climatically suitable area increased slightly. However, many areas retain potential as translocation sites (e.g. northern South Island), some areas become unsuitable (e.g. inland Canterbury) and/or involve extrapolation into novel climates (e.g. Northland).

Main Conclusion

SDMs incorporating locations of Holocene deposits and/or all past locations identified areas of critical habitat for tuatara under current and future climate scenarios that would not have been identified using contemporary occurrences only. Our results highlight the need to consider past locations when assessing habitat suitability for conservation translocations, both for tuatara and other relict species.


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Free pdf:

Charl D. Cilliers, Ryan T. Tucker, James L. Crowley & Lindsay E. Zanno (2021)
Age constraint for the Moreno Hill Formation (Zuni Basin) by CA-TIMS and LA-ICP-MS detrital zircon geochronology.
PeerJ 9:e10948
doi: https://doi.org/10.7717/peerj.10948
https://peerj.com/articles/10948/



The âmid-Cretaceousâ (~125--80 Ma) was punctuated by major plate-tectonic upheavals resulting in widespread volcanism, mountain-building, eustatic sea-level changes, and climatic shifts that together had a profound impact on terrestrial biotic assemblages. Paleontological evidence suggests terrestrial ecosystems underwent a major restructuring during this interval, yet the pace and pattern are poorly constrained. Current impediments to piecing together the geologic and biological history of the âmid-Cretaceousâ include a relative paucity of terrestrial outcrop stemming from this time interval, coupled with a historical understudy of fragmentary strata. In the Western Interior of North America, sedimentary strata of the TuronianâSantonian stages are emerging as key sources of data for refining the timing of ecosystem transformation during the transition from the late-Early to early-Late Cretaceous. In particular, the Moreno Hill Formation (Zuni Basin, New Mexico) is especially important for detailing the timing of the rise of iconic Late Cretaceous vertebrate faunas. This study presents the first systematic geochronological framework for key strata within the Moreno Hill Formation. Based on the double-dating of (U-Pb) detrital zircons, via CA-TIMS and LA-ICP-MS, we interpret two distinct depositional phases of the Moreno Hill Formation (initial deposition after 90.9 Ma (middle Turonian) and subsequent deposition after 88.6 Ma (early Coniacian)), younger than previously postulated based on correlations with marine biostratigraphy. Sediment and the co-occurring youthful subset of zircons are sourced from the southwestern Cordilleran Arc and Mogollon Highlands, which fed into the landward portion of the Gallup Delta (the Moreno Hill Formation) via northeasterly flowing channel complexes. This work greatly strengthens linkages to other early Late Cretaceous strata across the Western Interior.



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