Cretaceous Blind Snake from Brazil Fills Major Gap in Snake Evolution

Abstract

Summary Blind snakes (Scolecophidia) are minute cryptic snakes that diverged at the base of the evolutionary radiation of modern snakes. They have a scant fossil record, which dates back to the Upper Paleocene-Lower Eocene (∼56 Ma); this late appearance conflicts with molecular evidence, which suggests a much older origin for the group (during the Mesozoic: 160–125 Ma). Here we report a typhlopoid blind snake from the Late Cretaceous of Brazil, Boipeba tayasuensis gen. et sp. nov, which extends the scolecophidian fossil record into the Mesozoic and reduces the fossil gap predicted by molecular data. The new species is estimated to have been over 1 m long, much larger than typical modern scolecophidians (<30 cm). This finding sheds light on the early evolution of blind snakes, supports the hypothesis of a Gondwanan origin for the Typhlopoidea, and indicates that early scolecophidians had large body size, and only later underwent miniaturization.

Unveiling the elusive: X‐rays bring scolecophidian snakes out of the dark

“…The earliest reported fossils of the group were until recently restricted to the Paleogene with records reported from the Paleocene in Europe (Folie, 2007), Paleocene-Eocene boundary in north Africa (Augé & Rage, 2006), and possibly the Paleocene (Schiebout, Rigsby, Rapp, Hartnell, & Standhardt, 1987) and certainly the Oligocene (Mead, 2013) in North America. A recent report of a large-bodied scolecophidian, Boipeba tayasuensis, from the Cretaceous of Brazil pushes the material record of scolecophidians back into the late Mesozoic and suggests that the relatively small body size of extant scolecophidians is a derived condition (Fachini et al, 2020). This new record is consistent with recent genomic-scale data, which estimate the node containing Typhlopoidea, Anomalepididae, and Alethinophidia in the Cretaceous (Burbrink et al, 2020).…”

The Making of Calibration Sausage Exemplified by Recalibrating the Transcriptomic Timetree of Jawed Vertebrates

“…Parviraptor ,” including but not limited to the late Bathonian or earliest Callovian Eophis , the Kimmeridgian Diablophis and Portugalophis , and Parviraptor itself from around the Jurassic/Cretaceous (Tithonian/Berriasian) boundary. Traditionally regarded as representing the oldest anguimorphs, these fossils would calibrate Node 130, the split between Pan-Iguania [PN] and Anguimorpha; however, phylogenetic analyses following a redescription of much of the material have found it to constitute the oldest known pan-serpents, thus calibrating Node 129 ( Caldwell et al, 2015 ; Martill et al, 2015 ; by implication Conrad, 2017 ; accepted without analysis by Garberoglio et al, 2019 ; Simões et al, 2020 ; Schineider Fachini et al, 2020 ). As the Bathonian began 168.3 ± 1.3 Ma ago and ended 166.1 ± 1.2 Ma ago, i.e., with uncertainty ranges that overlap in the middle (ICSC), the suggestion of 167 Ma by Caldwell et al (2015) would then be a reasonable minimum age for this calibration.…”

Evolutionary treasures hidden in the West Indies: Comparative osteology and visceral morphology reveals intricate miniaturization in the insular genera Mitophis Hedges, Adalsteinsson, & Branch, 2009 and Tetracheilostoma Jan, 1861 (Leptotyphlopidae: Epictinae: Tetracheilostomina)

“…Blindsnakes, threadsnakes, and wormsnakes (traditionally known as "Scolecophidia") are of small size (mostly), fossorial and have extremely modified baupläne, which diverged at the base of the evolutionary radiation of modern snakes (Fachini et al, 2020;Greene, 1997;Vidal et al, 2010). Even though all living lineages, mainly from Anomalepididae and Leptotyphlopidae are small-sizedwith an adult maximum size ranging from 106 mm (Tetracheilostoma carlae; Adalsteinsson et al, 2009) to 460 mm (Rhinoleptus koniagui; Adalsteinsson et al, 2009)-recent fossil discoveries indicate that scolecophidians exhibited large sizes (1 m) in the Mesozoic and only later underwent an extreme body size reduction (Fachini et al, 2020). Such an extreme evolutionary size reduction-possibly due to miniaturization-most likely occurred independently in each of the main lineages (i.e., Anomalepididae, Leptotyphlopidae, and Typhlopoidea; Fachini et al, 2020).…”

“…The precloacal, cloacal, and caudal vertebrae are very conserved among "scolecophidians" (Fachini et al, 2020;Holman, 2000;List, 1966) in such a way that they are all dorsoventrally flattened, bear synapophyses with a single articular facet, lack a neural spine, and exhibit a rounded cotyle and condyle (Holman, 2000;Koch et al, 2019;List, 1966;Martins, Koch, et al, 2019;Pinto et al, 2015).…”

“…Rudimentary pelvic elements exhibit variable levels of degeneration among snakes, with such a level of degeneration most likely indicating their feasible functional aspect rather than their vestigial retention (Palci et al, 2020). Leptotyphlopids in general exhibit a low degree of degeneration of pelvic and hindlimb elements among snakes (Essex, 1927;List, 1966;Palci et al, 2020), with the presence of four ossified (and rarely cartilaginous) distinctive elements (ilium, ischium, pubis, and femur; Pinto et al, 2015;Palci, Hutchinon, Caldwell, Smith, & Lee, 2019;Martins et al, 2021). Both Mitophis (except for M. calypso) and Tetracheilostoma, however, seem to lack any trace of an ossified rudimentary pelvic element.…”