Felipe Chinaglia Montefeltro

Peirosauridae (Crocodyliformes, Notosuchia) is one of the fossil lineages of crocodyliforms ubiquitous in the Cretaceous deposits of the Bauru Basin. Here, we describe a new species of a longirostrine Peirosauridae from the Adamantina Formation (Bauru Basin, Late Cretaceous). The specimen consists of a partially preserved skull with a cranial roof, interorbital region, and fragments of the posterior portion of the rostrum, including the prefrontal and lacrimal; left hemimandible, with 14 alveoli and 12 teeth; and a single cervical rib fragment. The specimen is associated with Peirosauridae by three cranial synapomorphies, and it can be assigned to a new genus and species by presenting seven cranial and one tooth apomorphies. To clarify the position of the new taxon, an updated phylogenetic analysis was performed with increased sampling of taxa of Notosuchia, especially Peirosauridae, and phylogenetically relevant characters. Our results indicated the monophyly of Peirosauridae, formed by two main lineages, the oreinirostral and presumably terrestrial Peirosaurinae and the longirostrine and presumably semi‐aquatic Pepesuchinae. The recovering of both lineages as distinct entities was also reinforced through a morphospace analysis. Pepesuchinae were notable by exploring a position of the morphospace not explored by any other Notosuchia. Their longer rostra and the assumption of them being gradually specialized to aquatic habits reflects the unique diversity of these crocodyliforms through the Cretaceous deposits of South America and Africa.

The adaptive potential of plastic phenotypes relies on combined developmental responses. We investigated how manipulation of developmental conditions related to foraging mode in the fish Megaleporinus macrocephalus induces plastic responses at different levels: 1) functional modularity of skull bones, 2) biomechanical properties of the chondrocranium using Finite Element Models, 3) bmp4 expression levels, used as a proxy for molecular pathways involved in bone responses to mechanical load. We identified new modules in experimental groups, suggesting increased integration in specific head bone elements associated with the development of subterminal and upturned mouths, which are major features of Megaleporinus plastic morphotypes released in the lab. Plastic responses in head shape involved differences in the magnitude of mechanical stress, which seem restricted to certain chondrocranium regions. Three bones represent a ‘mechanical unit’ related to changes in mouth position induced by foraging mode, suggesting that functional modularity might be enhanced by the way specific regions respond to mechanical load. Differences in bmp4 expression levels between plastic morphotypes indicate associations between molecular signaling pathways and biomechanical responses to load. Our results offer a multilevel perspective of epigenetic factors involved in plastic responses, expanding our knowledge about mechanisms of developmental plasticity that originate novel complex phenotypes.

Speothos pacivorus is an extinct South American canid (Canidae: Cerdocyonina) from the Pleistocene of Lagoa Santa Karst, Central Brazil. This taxon is one of the hypercarnivore canids that vanished from the continent at the end of Pleistocene. Although all remains of Speothos pacivorus were collected in the 19th century by the Danish naturalist Peter W. Lund, few studies have committed to an in-depth analysis of the taxon and the known specimens. Here, we analyzed all biological remains of S. pacivorus hosted in the Peter Lund/Quaternary Collection at the Natural History Museum of Denmark, Copenhagen, by listing and illustrating all its specimens known to date. We also conducted a reconstruction of the holotype, an almost complete cranium, based on a µCT scan, producing an undeformed and crack-free three-dimensional model. With this data available we aim to foster new research on this elusive species.

Notosuchia is a large and diverse clade of Mesozoic crocodyliforms that thrived in continental environments especially during the Cretaceous of Gondwana. This clade has been the focus of several phylogenetic studies that led to the consensus of two main topological arrangements, mostly differing in the position of the clade Sebecidae: the sebecosuchian and sebecian hypotheses. In this manuscript we review the main phylogenetic definitions of several clades of notosuchians in the context of these hypotheses. As a result, besides the clade names previously established under the ICPN/Phylocode (including registration in RegNum) by Ruiz et al. (2021) (Notosuchia, Xenodontosuchia, Sphagesauria, Sphagesauridae) and Darlim et al. (2021a) (Baurusuchia, Baurusuchidae, Baurusuchinae, Pissarrachampsinae), eleven clade names have been registered and are defined in this contribution. Ten of these represent converted clade names (Uruguaysuchidae, Mahajangasuchidae, Peirosauridae, Itasuchidae, Ziphosuchia, Sphagesaurinae, Caipirasuchinae, Sebecia, Sebecosuchia, and Sebecia), while one represents a new clade name (Peirosauria). Furthermore, the definition of Xenodontosuchia is emended (unrestricted emendation) so that the name can be used in the context of a wider array of topologies.