New tools in dinosaur ichnology + Howesia (rhynchosaur) cranial anatomy + amphisbaenian evolution, phylogeny, and distribution + evolutionary timescales

[Ben Creisler]

Ben Creisler

bcre...@gmail.com

Recent papers:

Free pdf:

Ancheng Peng and Lida Xing (2026)
Classical Hypotheses and New Tools in Dinosaur Ichnology: A Review of Footprints with Geometric Morphometrics, Machine Learning and Biomechanics
Fossil Studies 4(3): 18
doi: https://doi.org/10.3390/fossils4030018
https://www.mdpi.com/2813-6284/4/3/18


Dinosaur footprints are among the most abundant trace fossils, but they are not direct records of anatomy, behaviour or faunal composition. They preserve locomotion, substrate interaction and occurrence data only after those signals have been filtered by foot anatomy, movement, sediment properties and preservation. Classical dinosaur ichnology has relied on two-dimensional outlines, linear and angular measurements, qualitative ichnotaxonomy and influential hypotheses about trackmaker identity, speed, social behaviour and evolutionary timing. Here we review how these hypotheses are being reassessed with three-dimensional digitisation, geometric morphometrics, supervised and unsupervised machine learning, and biomechanical simulation. We first consider how different footprint representations, including interpretive outlines, landmarks, silhouettes, depth maps and three-dimensional models, shape the questions that track data can answer. We then assess analytical approaches ranging from multivariate statistics and landmark-based classifiers to convolutional neural networks and β-variational autoencoders. Against this methodological background, we revisit four linked problem domains: ornithopod–theropod discrimination and the Grallator–Anchisauripus–Eubrontes plexus; speed and gait reconstruction; ecological and behavioural interpretations of track abundance, sauropod gauge and trackway arrangement; and macroevolutionary claims about body-size trends, functional morphotypes and avian-like pedal morphologies. Across these cases, newer methods rarely remove ambiguity. They more often show where classical interpretations are robust, where they depend on representation or prior labels, and where competing explanations remain hard to separate. We argue that footprint-based inference is strongest when tracks are treated as preservationally filtered products of anatomy, motion and substrate mechanics, and when they are integrated with skeletal data, experimental analogues and forward models in explicit, uncertainty-aware frameworks.

====

====

Free pdf:

Stephan N. F. Spiekman, Claire Browning, Muofhe Tshibalanganda, Debarati Mukherjee, Roger M. H. Smith, Anton Du Plessis & Frederik Wolvaardt (2026)
Micro-CT informed cranial anatomy of the early rhynchosaur Howesia browni, with implications for rhynchosaur skull evolution
Papers in Palaeontology 12(4): e70105
doi: https://doi.org/10.1002/spp2.70105
https://onlinelibrary.wiley.com/doi/10.1002/spp2.70105

Free pdf:
https://onlinelibrary.wiley.com/doi/epdf/10.1002/spp2.70105


Rhynchosaurs are unusual archosauromorph reptiles that lived between the Induan and early Norian (Early to early Late Triassic). They are characterized by their stocky build and broad skull with a beak-like premaxilla. This rather charismatic configuration is most clearly expressed in Late Triassic hyperodapedontine rhynchosaurids. However, the exact sequence in which morphological traits were acquired early in their evolution, leading to this body plan, remains incompletely resolved. Here, we present two new skulls of the early rhynchosaur Howesia browni, one of which is virtually completely preserved and analysed using high-resolution micro-computed tomography. The specimens derive from the Trirachodon-Kannemeyeria Subzone of the Cynognathus Assemblage Zone in South Africa (early Olenekian to early Anisian, Early to earliest Middle Triassic), which was previously considered to harbour three distinct early rhynchosaur taxa. On comparison two of the species are conspecific, with Eohyosaurus wolvaardti Butler et al. 2015 representing a junior synonym of Howesia browni Broom 1905. The new cranial information for Howesia browni corroborates that its skull morphology shows a distinctly intermediate condition between that of the non-rhynchosaurid rhynchosaur Mesosuchus browni and rhynchosaurids, sharing with the latter among other characteristics a beak-like premaxilla, marginal tooth plates, and an ‘anguli ori crest’. These findings provide the impetus for a refined review of the cranial evolution of Rhynchosauria. In contrast to other early archosauromorphs, rhynchosaurs exhibit a clear trend in their cranial evolution. This is likely to be related to their unique feeding strategy, which drove the evolution of an increasingly shortened and widened skull.

====

Roberta Graboski, Felipe G Grazziotin, Krister T Smith, Síria Ribeiro, Johannes Müller, Christy Anna Hipsley, Taran Grant, Alan Lemmon, Emily M Lemmon, John Measey, Tami Mott, Jean-François Trape, Guarino R Colli, Miguel T Rodrigues & Hussam Zaher (2026)
The present is (not necessarily) the key to the past: exploring the systematics, biogeography, and diversification of the amphisbaenians (Reptilia: Squamata)
Zoological Journal of the Linnean Society 207(3): zlag030
doi: https://doi.org/10.1093/zoolinnean/zlag030
https://academic.oup.com/zoolinnean/article-abstract/207/3/zlag030/8728452



Extant Amphisbaenia are distributed across Africa, the Americas, the Middle East, and the Mediterranean. Because of their fossorial habits, amphisbaenian biogeography was traditionally explained by vicariance. However, recent DNA studies emphasize the importance of transoceanic dispersal. Here, we provide the first phylogenomic analysis of Amphisbaenia using high-throughput sequence data (390 loci) with a comprehensive taxon sample. We present a time-calibrated phylogeny to infer biogeographic history and identify key cladogenetic events shaping present-day amphisbaenian diversity and distribution. Additionally, we evaluate head shape evolution and its association with speciation rates. We revise the group’s classification and present morphological diagnoses for some lineages, leading us to describe two new families and two new subfamilies from Africa. We also propose one new family from Cuba and one new subfamily from the Caribbean, and resurrect the subfamily Leposterninae and the genera Phractogonus and Typhloblanus. Our phylogeny suggests divergence between amphisbaenians and their sister-group lacertids occurred at ∼120 Mya, followed by early divergence of Rhineuridae from remaining amphisbaenians at ∼111 Mya. Considering their distinct skull morphologies, the round-headed shape is inferred to be ancestral for all high-level groups. The shovel-headed shape appeared more recently and is linked to the highest evolutionary rates, suggesting it enabled rapid speciation and habitat dispersal.

=====

=====

Free pdf:

Tom Carruthers (2026)
Interactions between phylogenetic trees and fossils when estimating evolutionary timescales
Journal of Evolutionary Biology, voag055,
doi: https://doi.org/10.1093/jeb/voag055
https://academic.oup.com/jeb/advance-article/doi/10.1093/jeb/voag055/8728734


I explore the impact of extinct lineages and limited morphological character data on the expected delay between the origin time of a clade and the age of its oldest known fossil (the clade-fossil delay). The size of the clade-fossil delay, and variation in its size between clades, fundamentally impacts the extent to which the fossil record is informative about the ages of different clades. The clade-fossil delay is thus a crucial quantity when estimating the timing of branching events in phylogenetic trees (divergence time estimation). I show that both extinct lineages and limited morphological character data increase the clade-fossil delay, especially in datasets with few fossils, which is particularly common when estimating divergence times in flowering plants. Though linked to taphonomic biases, these results are distinct in that they are underpinned by interactions between extinct lineages, limited morphological data, and the nested structure of phylogenetic trees. I discuss the likely impacts of these findings on divergence time analyses and the evolutionary studies that depend on them, and suggest that both a fundamental re-appraisal of the purpose of divergence time estimation, alongside the development of new methods, is required.