Producción CyT
Congreso
Autoría
Mark J Powers
;
GARBEROGLIO, FERNANDO FABIO
;
Caldwell, Michael W.
Fecha
2024
Editorial y Lugar de Edición
Society of Vertebrate Paleontology
Resumen
Información suministrada por el agente en
SIGEVA
Madtsoiidae is an extinct clade of snakes united by several vertebral characters. The oldest specimens are from the Late Cretaceous of Gondwana. However, they reached a nearly global distribution by the Eocene, achieving large body sizes and are typically collected from fluvial and paralic sedimentary units. The first sets of vertebrae discovered were thought to belong to a large boid. However, recognition of several key features such as the absence of accessory prezygapophyseal proce...
Madtsoiidae is an extinct clade of snakes united by several vertebral characters. The oldest specimens are from the Late Cretaceous of Gondwana. However, they reached a nearly global distribution by the Eocene, achieving large body sizes and are typically collected from fluvial and paralic sedimentary units. The first sets of vertebrae discovered were thought to belong to a large boid. However, recognition of several key features such as the absence of accessory prezygapophyseal processes, the presence of laterally expanded para-diapophyses and parazygantral foramina led to the proposal of a monophyletic Madtsoiidae, named after the type species Madtsoia bai from Chubut Province, Argentina. Due to cranial material being quite rare, most named taxa within Madtsoiidae are described from isolated vertebrae, or segments of articulated vertebrae. Because relatively complete madtsoiids are rare, species diagnoses, and phylogenetic relationships are described primarily from vertebral characters. Snake vertebral columns can show considerable variation across the possible 150-400 vertebrae. Variability of madtsoiid synapomorphies across the vertebral column has not been critically assessed due to the relatively short series of articulated vertebrae and the scarcity of cervical (anterior trunk) and caudal (post-cloacal) vertebrae.Additionally, the putative synapomorphies of Madtsoiidae have not been systematically surveyed across other fossil lineages (e.g., Palaeophiidae). An articulated series of cervicals from upper Eocene deposits of the Divisadero Largo Formation in the Cuyo Basin of the Mendonza province, Argentina, are referred to Madtsoia sp. based on putative madtsoiid synapomorphies (e.g., parazygantral foramina), age (Mid-Late Eocene) and proximity to the holotype locality. We report here on the variability of these “synapomorphies” across a single vertebral series and see this as demonstrative of problematic degrees of within column variation as well as individual variation. This variability becomes more problematic when diagnosing isolated vertebrae as “madtsoiid”. Comparisons with palaeophiids, fossil taxa such as Boavus, and modern snake taxa demonstrate a much broader expression of putative madtsoiid synapomorphies. These observations reinforce the poor utility of vertebral characters alone in snake phylogenetics and stress the importance of relatively complete specimens in constructing taxonomic diagnoses to be used in subsequent analyses.
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Palabras Clave
PhylogenyMadtsoiaSnakesMadtsoiidae