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Pleurodonta is an ancient, diverse clade of iguanian lizard distributed primarily in the Western Hemisphere. Although the clade is a frequent subject of systematic research, phylogenetic resolution among the major pleurodontan clades is elusive. That uncertainty has complicated the interpretations of many fossil pleurodontans. I describe a fossil skull of a pleurodontan lizard from the Palaeogene of Wyoming that was previously allocated to the puzzling taxonAciprion formosum, and provide an updated morphological matrix for iguanian lizards. Phylogenetic analyses using Bayesian inference demonstrate that the fossil skull is the oldest and first definitive stem member of Crotaphytidae (collared and leopard lizards), establishing the presence of that clade in North America during the Palaeogene. I also discuss new or revised hypotheses for the relationships of several early pleurodontans. In particular, I examine potential evidence for crown-Pleurodonta in the Cretaceous of Mongolia (Polrussia), stem Pleurodonta in the Cretaceous of North America (Magnuviator) and a stem anole in the Eocene of North America (Afairiguana). I suggest that the placement of the fossil crotaphytid is stable to the uncertain phylogeny of Pleurodonta, but recognize the dynamic nature of fossil diagnosis and the potential for updated systematic hypotheses for the other fossils analysed here.
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The oldest dairoidid crab (Decapoda, Brachyura, Parthenopoidea) from the Eocene of Spain
Abstract Eubrachyurans, or ‘higher’ true crabs, are the most speciose group of decapod crustaceans and have a rich fossil record extending into the Early Cretaceous. However, most extant families are first found in the fossil record in the Palaeogene, and particularly in the Eocene. Unfortunately, fossils of many early eubrachyuran groups are often fragmentary, and only a few studies have combined extinct and extant taxa in a phylogenetic context using different optimality criteria. Here, we report the dairoidid crabPhrynolambrus sagittalissp. nov., an enigmatic eubrachyuran from the upper Eocene of Huesca (northern Spain), whose completeness and exquisite preservation permit examination of its anatomy in a phylogenetic context. Dairoidids have previously been considered among the oldest stone crabs (Eriphioidea) or elbow crabs (Parthenopoidea), two disparate and distantly related groups of true crabs living today. Mechanical preparation and computed tomography of the fossil material revealed several diagnostic features that allow a detailed comparison with families across the crab tree of life, and test hypotheses about its phylogenetic affinities.Phrynolambrus sagittalisis the first record of the genus in the Iberian Peninsula, and represents one of the oldest crown parthenopoidean crabs worldwide, expanding our knowledge of the biogeographical distribution of elbow crabs during the Palaeogene, as well as their early origins, anatomical diversity and systematic affinities. Understanding the disparity of Eocene eubrachyurans is pivotal to disentangling the systematic relationships among crown families, and interpreting the spatio‐temporal patterns leading to the evolution of modern faunas.
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- Award ID(s):
- 1856679
- PAR ID:
- 10442948
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Papers in Palaeontology
- Volume:
- 9
- Issue:
- 3
- ISSN:
- 2056-2799
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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