Phylogeny, biogeography and classification of the snake superfamily Elapoidea: a rapid radiation in the late Eocene

Abstract

The snake superfamily Elapoidea presents one of the most intransigent problems in systematics of the Caenophidia. Its monophyly is undisputed and several cohesive constituent lineages have been identified (including the diverse and clinically important family Elapidae), but its basal phylogenetic structure is obscure. We investigate phylogenetic relationships and spatial and temporal history of the Elapoidea using 94 caenophidian species and approximately 2300-4300 bases of DNA sequence from one nuclear and four mitochondrial genes. Phylogenetic reconstruction was conducted in a parametric framework using complex models of sequence evolution. We employed Bayesian relaxed clocks and Penalized Likelihood with rate smoothing to date the phylogeny, in conjunction with seven fossil calibration constraints. Elapoid biogeography was investigated using maximum likelihood and maximum parsimony methods. Resolution was poor for early relationships in the Elapoidea and in Elapidae and our results imply rapid basal diversification in both clades, in the late Eocene of Africa (Elapoidea) and the mid-Oligocene of the Oriental region (Elapidae). We identify the major elapoid and elapid lineages, present a phylogenetic classification system for the superfamily (excluding Elapidae), and combine our phylogenetic, temporal and biogeographic results to provide an account of elapoid evolution in light of current palaeontological data and palaeogeographic models.

Molecular phylogeny of advanced snakes (Serpentes, Caenophidia) with an emphasis on South American Xenodontines: a revised classification and descriptions of new taxa

“…Some other molecular studies (e.g., Lawson et al, 2005;Kelly et al, 2009) found a radically different phylogenetic position for xenodermatines based on molecular sequences for Oxyrhabdium, which is typically included within this group. Xenodermatinae is supported by a putative synapomorphy: a concave nasal shield that accommodates the nostril (McDowell, 1987).…”

“…In neither analysis does the position of Prosymna receive significant support. Similarly, although Kelly et al (2009) provided strong support for a clade (Pseudaspis + Pythonodipsas), the relationship of that clade to other elapoids was ambiguous. In the taxonomically broader phylogenetic analysis by Lawson et al (2005), the strict consensus parsimony tree shows Prosymna + Oxyrhabdium as a sister clade to the Elapidae; Psammodynastes as the sister group of Atractaspis; and Pseudaspis + Pythonodipsas as a clade more closely related to the Lamprophiidae than to any other elapoid group.…”

“…Subsequently, Pinou et al (2004) applied the resurrected name "Elapoidea" to a clade comprising Atractaspis + Elapidae. "Elapoidea" has subsequently been used for "Clade A" of Lawson et al (2005) in several molecular phylogenetic studies (Vidal et al, 2007(Vidal et al, , 2008; Kelly et al, 2009; see also our results below). Clade B of Lawson et al (2005) was referred to as "Colubroidea" by Pinou et al (2004) and subsequent authors.…”

“…On the other hand, Vidal et al (2008) considered Prosymna, Pseudaspis, Pythonodipsas, Buhoma, Psammodynastes, Micrelaps, and Oxyrhabdium to represent elapoid lineages with unresolved affinities, and suggested that additional sequencing was needed to better resolve their affinities. Indeed, Prosymna falls into radically different phylogenetic positions in the studies of Vidal et al (2008), in which it clusters with Atractaspididae + Pseudoxyrhophiidae + Lamprophiidae, and Kelly et al (2009), in which it is nested within the Psammophiidae + Pseudoxhyrhophiidae. In neither analysis does the position of Prosymna receive significant support.…”

“…Prosymnidae and Pseudaspididae: Kelly et al (2009) proposed new names for several "clades" within Elapoidea (see below). They recognized a new family, Prosymnidae, including only the genus Prosymna based on the fact that Prosymna appeared in all their analyses "at the same hierarchical level as other major clades" and thus should be accommodated in a distinct family.…”