Two new Royal Society papers suffer from taxon exclusion

Gutarra et al. 2019
tested the effects of several body plans on the hydrodynamic drag of simplified 3D digital ichthyosaurs. They reported, “Our results show that morphology did not have a major effect on the drag coefficient or the energy cost of steady swimming through geological time.”

Unfortunately
the Gutarra team included the basal sauropterygian ichthyosaur-mimic Cartorhynchus as their basal taxon, ignoring the following four valid ichthyosaur basal taxa.

  1. Wumengosaurus
  2. any hupehsuchid
  3. Thaisaurus
  4. Xinminosaurus

Given the Gutarra et al. similar results
for all included digitally generated taxa, it would have been instructive to test at least one of these basal taxa or perhaps outgroup taxa from the Mesosauria and/or Thalattosauria in order to set a baseline. Co-author professor MJ Benton has been reprimanded for excluding taxa several times before, and doggone it, he did it again.


Halliday et al. 2019
“supports a Late Cretaceous origin of crown placentals with an ordinal-level adaptive radiation in the early Paleocene, with the high relative rate permitting rapid anatomical change without requiring unreasonably fast molecular evolutionary rates.” 

By contrast
the large reptile tree (LRT, 1413 taxa) nests several placental taxa (like multituberculates) in the Jurassic with placental origins likely in the Late Triassic very soon after the origin of Mammalia.

Halliday’s team differentiates extant placentals from several extinct eutherians,
while the LRT finds only one extant taxa, the arboreal didelphid Caluromys, in the Eutheria outside of the Placentalia.

Halliday’s team cites the Luo et al. 2011 report
of “a Jurassic eutherian mammal” (= Juramaia) with reservations. In the LRT Juramaia nests with basal prototherians, not eutherians.

None of Halliday’s published work
matches the topology of the LRT. The Halliday team nests highly derived hedgehogs, elephants and armadillos as a closely related clade at the base of their cladogram of extant placentals.

By contrast and employing more taxa
the LRT documents the evolution of three clades of basal placentals, like arboreal civets, bats, dermopterans, pangolins and tree shrews (Primates + Glires), from arboreal marsupials, like Caluromys. 

Evolution: small changes over time.
The editors and referees approved Halliday’s ‘traditional’ topology. Someone should have checked results for relationships that minimize differences between recovered sisters. More taxa and avoiding genetic scoring would have helped.

Halliday’s study supports several invalidated genetic clades,
including Atlantogenata (anteaters + elephants and kin), Boreotheria (mice + whales + humans and kin), and Afrotheria (elephant shrews + elephants and kin). Even so, editors, paleoworkers and referees approved these untenable and refuted relationships.

That’s why the LRT is here,
to lift the covers and show you untenable traditional relationships, then to offer a tree topology in which all included taxa document a gradual accumulation of derived traits.


References
Gutarra S, Moon BC, Rahman IA, Palmer C, Lautenschlager S, Brimacombe AJ, and Benton MJ 2019. Effects of body plan evolution on the hydrodynamic drag and energy requirements of swimming in ichthyosaurs. Proc. R. Soc. B 286: 20182786. http://dx.doi.org/10.1098/rspb.2018.2786
Halliday TJD, dos Reis M, Tamuri AU, Ferguson-Gow H, Yang Z and Goswami A 2019. Rapid morphological evolution in placental mammals post-dates the origin of the crown group. Proc. R. Soc. B 286: 20182418. http://dx.doi.org/10.1098/rspb.2018.2418

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