Wednesday, January 26, 2022

[Paleontology • 2021] The Fossil Record and Phylogeny of South American Horned Frogs (Anura, Ceratophryidae)

in Gómez & Turazzini, 2021.

South American horned frogs (Ceratophryidae), with their large heads, wide gapes and fang-like teeth, are among the most charismatic, best-known and well-studied neobatrachian anurans. The family comprises 12 extant species with hyperossified skulls and has a relatively rich fossil record, particularly in the Pampas, which dates back to the late Miocene. However, several records have been overlooked in recent summaries, and many taxonomic assignments remain indeterminate or are questionable and have yet to be tested within a quantitative phylogenetic framework. Here we provide a complete up-to-date survey of the palaeontological record of Ceratophryidae, including some remarkable new records. We also tested their systematic position through comprehensive phylogenetic analyses based on osteological data, providing several synapomorphies for all relevant nodes. Finally, we discuss these integrated data in relation to divergence time estimates, and propose a set of fossil calibrations that provide hard minimum bounds for crown-group Ceratophryidae and the subclades within it, and illuminate the acquisition of polyploidy within the group.

Keywords: Ceratophrys, Lepidobatrachus, Chaco, Pampas, phylogenetics, osteology, calibration point

Anura Fischer, 1813 
Neobatrachia Reig, 1958 
Nobleobatrachia Frost, Grant, Faivovich, Bain, Haas, Haddad, de Sá, Channing, Wilkinson, Donnellan, Raxworthy, Campbell, Blotto, Moler, Drewes, Nussbaum, Lynch, Green & Wheeler, 2006 

Ceratophryidae Tschudi, 1838 

Type genus: Ceratophrys Wied-Neuwied, 1824.

Chacophrys Reig & Limeses, 1963

Chacophrys pierottii (Vellard, 1948) 

 Ceratophrys ameghinorum. MACN Pv 14318 (holotype)

Ceratophrys Wied-Neuwied, 1824 

Ceratophrys ameghinorum Fernicola, 2001 

Ceratophrys aurita (Raddi, 1823)

Ceratophrys ornata (T. Bell, 1843) 

Lepidobatrachus Budgett, 1899 

Lepidobatrachus australis Nicoli, 2015 

 The oldest record of South American horned frogs dates back to the late Miocene and represents total-group Ceratophrys, providing a hard minimum bound for Ceratophryidae. However, other Miocene records are fragmentary or show morphologies not represented among extant species, obscuring their phylogenetic relationships. The known fossil record of Ceratophrys is relatively rich but is restricted mostly to the clade comprising species with a dorsal shield, including Ce. ornata and Ce. aurita. Our phylogenetic analyses consistently recovered the extinct Ce. ameghinorum and its kin, including two putative new forms, as more closely related to Ce. aurita than to any other extant species. The known fossil record of Lepidobatrachus is sparse and likely restricted to the Pliocene, but shows that the total group inhabited regions outside its present day Chacoan distribution. Phylogenetic analyses recovered the Pliocene L. australis and a new form from western Argentina as part of total-group Lepidobatrachus, but lying outside the crown-group. Crown-group Lepidobatrachus and Chacophrys have no known fossil record to date. Extinct taxa that remain valid are mostly from the Pliocene of Buenos Aires Province, whereas almost all of the Quaternary record that can be confidently assigned to species level represents extant taxa. Integration of ploidy data from extant species and fossils in our phylogenetic framework suggests that in Ce. ornata and Ce. aurita octoploidy arose through tetraploidy late in the Quaternary.

Raúl Orencio Gómez and Guillermo Fidel Turazzini. 2021. The Fossil Record and Phylogeny of South American Horned Frogs (Anura, Ceratophryidae). Journal of Systematic Palaeontology. 19(2); 91-130. DOI: 10.1080/14772019.2021.1892845