[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

[dinosaur] Kallokibotion redescribed + Triassic coprolites from Brazil + origin of endothermy

Some recent and not so recent papers:


Online more than a month ago but not yet mentioned:

Adán Pérez-García & Vlad Codrea (2017)

New insights on the anatomy and systematics of Kallokibotion Nopcsa, 1923, the enigmatic uppermost Cretaceous basal turtle (stem Testudines) from Transylvania.

Zoological Journal of the Linnean Society, zlx037, (advance online publication)

doi: https://doi.org/10.1093/zoolinnean/zlx037


Kallokibotion is a basal turtle (stem Testudines) described almost a century ago from generally poorly preserved specimens, from the Maastrichtian of the Haţeg Basin (Romania). A revision of these specimens, performed almost 25 years ago, allowed a better understanding of the taxon. Kallokibotion has remained an enigmatic form because of the limited number of available characters. However, it has frequently been included in general phylogenetic hypotheses of relationships among Testudinata or among basal forms. The information in these analyses has been based on the classic material because, until now, no new specimens had been figured and described in detail. Its phylogenetic position has been under discussion. Well-preserved new material is presented here. These specimens not only reveal detailed cranial and postcranial elements poorly known until now, refuting previous hypotheses about the anatomy of this taxon, but also allow us to identify numerous hitherto unknown characters. Thus, Kallokibotion is recognized as one of the best-characterized stem Testudines. A new diagnosis for its only known species, Kallokibotion bajazidi, is proposed. The incorporation of new information in several phylogenetic analyses shows  as the sister taxon of the crown Testudines.


Heitor Francischini, Paula Dentzien-Dias & Cesar L. Schultz (2017)
A fresh look at ancient dungs: the Brazilian Triassic coprolites revisited.
Lethaia (advance online publication)
DOI: 10.1111/let.12251

Terrestrial tetrapod coprolites are abundant in the Middle to Late Triassic of southern Brazil, but only few specimens have been described in just a couple of papers. Here we revisit the already-known specimens and describe new materials, including their size, shape, external modifications, matrix composition and rare inclusions. Regarding size and shape, the measurements of 152 specimens show that the Triassic coprolites of Brazil follow a normal distribution, in which length and width are positively correlated variables, so that they are not useful for taxonomic purposes. Notwithstanding, two ichnotaxa, Santamariacopros elongatus and Rhynchocopros soutoi, were previously described from the Middle/Upper Triassic Santa Maria Formation, based mainly on morphological (length/width ratio) and preservational features, but we discuss here the validity of such taxa. Once the Santa Maria Formation encompasses at least three tetrapod Assemblage Zones (AZ), Dinodontosaurus AZ, Santacruzodon AZ and Hyperodapedon AZ (from the oldest to the youngest, respectively), it is difficult to attribute these coprolites to any specific animal producers. In addition, the rarity of inclusions and the carbonated composition of the coprolites, related to early diagenetic processes, complicate this attribution too. Nevertheless, some rare inclusions as a hair-like structure and a parasite egg were found in this study. Although the coprotaxonomy fails to represent the Santa Maria Formation coprolites and the recognition of their producers is a problematic task, these fossil dungs are important elements in the knowledge of the Middle to Late Triassic environments of southern Brazil.


Jan Werner & Eva Maria Griebeler (2017)

Was endothermy in amniotes induced by an early stop in growth during ontogeny?

The Science of Nature (advance online publication) 

DOI: https://doi.org/10.1007/s00114-017-1513-1



Endothermy and its evolution are still an unresolved issue. Here, we present a model which transforms an ectothermic amniote (ancestor) into a derived amniote (descendant) showing many characteristics seen in extant endothermic birds and mammals. Consistent with the fossil record within the ancestral lineages of birds and mammals, the model assumes that mutations in genes which get active during ontogeny and affect body growth resulted in a reduced asymptotic body size and an early growth stop of the descendant. We show that such a postulated early growth stop in the descendant simultaneously increases the growth rate and metabolic rate, and also changes six life history traits (offspring mass, annual clutch/litter mass, number of offspring per year, age and mass at which sexual maturity is reached, age at which the individual is fully grown) of the descendant compared to a similar-sized ancestor. All these changes coincide with known differences between recent ectothermic and endothermic amniotes. We also elaborate many other differences and similarities in biological characteristics supporting the early growth stop. An early stop in growth during ontogeny thus could have played a key role in the evolution of endothermy within the reptilia and therapsids. It generated variability in characteristics of ancestral ectotherms, which was subject to natural selection in the past and resulted in many adaptations linked to endothermy in today’s birds and mammals.


Virus-free. www.avg.com