Caecilians are predominantly burrowing, elongate, limbless amphibians that have been relatively poorly studied. Although it has been suggested that the sturdy and compact skulls of caecilians are an adaptation to their head-first burrowing habits, no clear relationship between skull shape and burrowing performance appears to exist. However, the external forces encountered during burrowing are transmitted by the skull to the vertebral column, and, as such, may impact vertebral shape. Additionally, the muscles that generate the burrowing forces attach onto the vertebral column and consequently may impact vertebral shape that way as well. Here, we explored the relationships between vertebral shape and maximal in vivo push forces in 13 species of caecilian amphibians. Our results show that the shape of the two most anterior vertebrae, as well as the shape of the vertebrae at 90% of the total body length, is not correlated with peak push forces. Conversely, the shape of the third vertebrae, and the vertebrae at 20% and 60% of the total body length, does show a relationship to push forces measured in vivo. Whether these relationships are indirect (external forces constraining shape variation) or direct (muscle forces constraining shape variation) remains unclear and will require quantitative studies of the axial musculature. Importantly, our data suggest that mid-body vertebrae may potentially be used as proxies to infer burrowing capacity in fossil representatives.
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RBINS Staff Publications 2022
We present an updated, subjective list of the extant, non-marine ostracod genera and species of the world, with their distributions in the major zoogeographical regions, as well as a list of the genera in their present hierarchical taxonomic positions. The list includes all taxa described and taxonomic alterations made up to 1 July 2018. Taxonomic changes include 17 new combinations, 5 new names, 1 emended specific name and 11 new synonymies (1 tribe, 4 genera, 6 species). Taking into account the recognized synonymies, there are presently 2330 subjective species of non-marine ostracods in 270 genera. The most diverse family in non-marine habitats is the Cyprididae, comprising 43.2% of all species, followed by the Candonidae (29.0%), Entocytheridae (9.1%) and the Limnocytheridae (7.0%). An additional 13 families comprise the remaining 11.8% of described species. The Palaearctic zoogeographical region has the greatest number of described species (799), followed by the Afrotropical region with 453 species and the Nearctic region with 439 species. The Australasian and Neotropical regions each have 328 and 333 recorded species, respectively, while the Oriental region has 271. The vast majority of non-marine ostracods (89.8%) are endemic to one zoogeographical region, while only six species are found in six or more regions. We also present an additional list with ‘uncertain species’, which have neither been redescribed nor re-assessed since 1912, and which are excluded from the main list; a list of taxonomic changes presented in the present paper; a table with the number of species and % per family; and a table with numbers of new species described in the 20-year period between 1998 and 2017 per zoogeographical region. Two figures visualize the total number of species and endemic species per zoogeographical region, and the numbers of new species descriptions per decade for all families and the three largest families since 1770, respectively.
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RBINS Staff Publications 2019
