Corallus

Head, JJ, 2015, Fossil calibration dates for molecular phylogenetic analysis of snakes 1: Serpentes, Alethinophidia, Boidae, Pythonidae, Palaeontologia Electronica 18, pp. 1-17 : 7

CORALLUS

Node Calibrated. Divergence between total clade Corallus and the total clade ( Chilabothrus +( Epicrates + Eunectes )).

Fossil Taxon. Corallus priscus Rage, 2001 .

Specimen. DGM 1332 - R precloacal vertebra (holotype) .

Additional Materials. 74 precloacal vertebrae.

Phylogenetic Justification. Corallus priscus was assigned to the genus Corallus by Rage (2001) on the basis of: horizontal zygapophyseal articular facets, vaulted neural arch, and a tall neural spine. Additionally, C. priscus shares small, irregularly occurring paracotylar foramina with extant species of the genus. The combination of neural spine height and anteroposterior width, bi-angled interzygapophyseal ridges, and zygosphene shape make specimens of C. priscus indistinguishable from extant Corallus .

Minimum Age. 50.2 Ma.

Soft Maximum Age. ~64 Ma ( Woodburne et al., 2014).

Age Justification. Corallus priscus was recovered from fissure fills in travertine deposits at the locality of São José de Itaboraí in Rio de Janeiro, Brazil. The travertine layers are unconformably overlain by a basalt flow dated at 52.6 ± 2.4 Ma ( Riccomini and Rodrigues-Francisco, 1992; Gomes Sant’Anna and Riccomini, 2001; Woodburne et al., 2014), which provides a hard minimum age for the taxon. The soft maximum age is the same as for Titanoboa .

Discussion. The fossil record of Corallus from Itaboraí represents the oldest record of an extant boid genus, and constrains the divergence of Neotropical Boinae to no younger than approximately 50 Ma. Molecular phylogenetic analyses place Boa constrictor as the sister taxon to Corallus + Chilabothrus +( Eunectes + Epicrates ) ( Burbrink, 2005; Pyron et al., 2013; Reynolds et al., 2013, 2014). The first occurrence of Boa ( Figure 1 ) and molecular topologies thus implies an approximately 19 Ma unrecovered history of the genus between the maximum age of the Barrancan SALMA and the hard minimum age for Corallus ( Head et al., 2012) , assuming Titanoboa is a stem boine.

Figures

FIGURE 1. Time-calibrated phylogeny of Serpentes based on Pyron et al. (2013) and Reynolds et al. (2014). Numbers represent calibrated nodes in text. Fossil taxa are the calibration points for their respective nodes. Thickened bars represent well-sampled, taxonomically resolved stratigraphic distributions for the sister taxa to Pan-Serpentes and snake lineages whose first occurrences are determined by older sister taxa. Thin bars represent estimated stratigraphic distributions for taxa with poorly resolved fossil records, or no published fossil record (names in grey). “Scolecophidia” represents a paraphyletic grade with respect to Alethinophidia (see text).