Radiation and Divergence Times of BatoideaCitation for this article: Villalobos-Segura, E., and C. J. Underwood. 2020. Radiation and divergence times of Batoidea. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2020.1777147.

Abstract

We present a time-scaled analysis based on morphological characters to estimate the divergence ages for the major batoids clades. Two approaches were used: Tip-dating, which allows the extinct taxa to be included as terminals, assessing the phylogenetic relations and their divergence time simultaneously; and basic and minimum branch length ("a posteriori" methods) that date a pre-existing unscaled topology, given a set of stratigraphic data for the taxa involved.We used stratigraphic indexes to compare the divergence ages recovered by both methods. The tip-dating approach obtained a more resolved topology and slightly better stratigraphic indexes scores than the other methods. Overall the tip-dating analysis recovered slightly earlier divergence ages than the rest of the time dating analyses and the known fossil record of the groups. However, these divergence ages were not as old as those estimated by molecular analysis. Our results suggest the diversity increase through the Late Jurassic-Early Cretaceous might not be gradual, and that Early Cretaceous diversity could be significantly higher. As several divergence events are placed in the Early Cretaceous, there is a suggestion that an active period of cladogenesis leads to the Late Cretaceous high diversity. The last divergence events recovered by the present analysis occurred in the Paleogene and led to the extant groups of batoids.

The Phylogeny of Rays and Skates (Chondrichthyes: Elasmobranchii) Based on Morphological Characters Revisited

“…While the relationships between selachimorphs and batomorphs are not completely resolved in the present analysis, our character and taxon sampling presents a persistent placement of most of the fossil taxa within certain clades (orders and families), and their consistent similar relationships in all tree topologies—often similar to those previously hypothesized (e.g., [ 23 , 24 , 41 , 127 ])—is promising and indicates that the inclusion of more fossil taxa in the present matrix likely will not cause loss of resolution, therefore suggesting that a strong phylogenetic signal can be recovered from fossil taxa.…”

Reproductive Anatomy of Chondrichthyans: Notes on Specimen Handling and Sperm Extraction. I. Rays and Skates

“…Overall, the general morphological structure of the female reproductive system is well maintained across all the species studied (Figure 4). This anatomical resemblance was particularly remarkable between skates (species from the genus Raja) (Figure 4A) and the marbled electric ray T. marmorata (Figure 4E), probably because of the close evolutionary relationship between these two plesiomorphic groups [34]. Both groups have the same disposition of the basic anatomical structures, but with a clear divergence in the size of the oviducal gland.…”

“…Although being closed from an evolutionary perspective [34], some variations exist in the morphology of the urogenital system of the common eagle ray M. aquila (Figure 6C) and the bull ray A. bovinus (Figure 6D). M. aquila possess four different pores in the urogenital papilla, with the upper two (slightly bigger) leading to the seminal vesicles.…”

Feeding on clean food? Potential effects of electric organ discharges by Torpedo spp. (Torpediniformes: Torpedinidae) on their trophically transmitted parasites

“…These figures were placed on a cladogram of the Batoidea and interpreted visually. The cladogram included all genera for which parasitological data were available and was built based on the most recent phylogenetic studies using morphology and molecular markers (Aschliman et al 2012;Gaitán-Espitia et al 2016;Last et al 2016;Da Cunha et al 2017;Marramà et al 2018;Villalobos-Segura & Underwood 2020).…”