Batrachia (Caudata + Salientia) = Amphibians (= extant Frogs + Salamanders) Marjanovic discusses Triadobatrachus from the Early Triassic (Olenekian, 249mya) and concludes that 249 mya “is a perfectly adequate hard minimum age for this calibration point.” And “290mya may be a defensible soft maximum value.”
After adding Triadobatrachus (Fig. 1) to the large reptile tree (LRT, 1631+ taxa), Gerobatrachus (Early Permian, 300mya) mentioned once by Marjanovic, nests basal to the few tested extant frogs and salamanders. So, 300mya is pretty close to his estimate of 290mya.
Chondrichthyes (Holocephalii + Elasmobranchii)
= (ratfish + sharks and skates) Marjanovic reports, “By current understanding (Frey et al., 2019), the oldest known crown-chondrichthyan is the stem elasmobranch Phoebodus fastigatus from the middle Givetian. The Givetian, part of the Middle Devonian, …so I propose 385 Ma as the hard minimum age of the chondrichthyan crown-group.”
By contrast, the LRT recovers the whale shark + manta ancestor, Loganellia (Early Silurian, 440mya; Fig. 3) as the oldest known ancestor of sharks and other fish. Sturgeons are more primitive, and therefore must be older, but Ordovician sturgeon and osteostracan fossils have not been found. Taxon inclusion recovers these novel interrelationships.
Marjanovic reports, “There is not as much interest in phylogeny among specialists of early elasmobranchs than among specialists of early mammals or early dinosaurs.” The LRT does not have that problem. Enigmas are answered with this powerful tool that works well by avoiding tooth-only taxa.
Marjanovic considers the clade Batoidea (skates + rays) to be monophyletic.
In the LRT, so far, three origins for ray-like basal tetrapods have been recovered based on taxon inclusion.
Marjanovic considers the clade Neopterygii (Holosteomorpha + Teleosteomorpha) = (bowfins and gars + other teleosts or bony fish) to be monophyletic.
In the LRT, this hypothesis of relationships has been invalidated.
Marjanovic reports, “I cite 228 references for calibration purposes.”
In the LRT, I’m not sure how many citations I cite for 1631+ taxa, but once again, adding taxa brings new insights to hypothetical interrelationships. Marjanovic was testing the results of a previous publication, but should have done so with a greater authority, with more taxa and with no reference whatsoever to genomics.
Tomorrow: something new.
Marjanovic D 2019. Recalibrating the transcriptomic timetree of jawed vertebrates.
bioRxiv 2019.12.19.882829 (preprint)