Célik and Phillips 2020 attempted to
understand the phylogenetic order of basal mammals by excluding traits. They wrote, “Excluding these character complexes brought agreement between anatomical regions and improved the confidence in tree topology.”
Those issues aside, taxon exclusion mars this study.
The Célik and Phillips cladogram shuffled together unrelated taxa compared to the large reptile tree (LRT, 1737+ taxa). They cladogram (Fig. 1) mixed pre-mammals with placentals and marsupials chiefly due to taxon exclusion.
By employing so many taxa,
the LRT minimizes taxon exclusion and resolves such issues as the Multituberculata / Haramiyida problem. These taxa nest within Glires in the Placentalia in the LRT. Glires is not otherwise well represented in the Célik and Phillips cladogram.
From the abstract
“The evolutionary history of Mesozoic mammaliaformes is well studied. Although the backbone of their phylogeny is well resolved, the placement of ecologically specialized groups has remained uncertain. Functional and developmental covariation has long been identified as an important source of phylogenetic error, yet combining incongruent morphological characters altogether is currently a common practice when reconstructing phylogenetic relationships.”
“Ignoring incongruence may inflate the confidence in reconstructing relationships, particularly for the placement of highly derived and ecologically specialized taxa, such as among australosphenidans (particularly, crown monotremes), haramiyidans, and multituberculates. The alternative placement of these highly derived clades can alter the taxonomic constituency and temporal origin of the mammalian crown group.”
“Based on prior hypotheses and correlated homoplasy analyses, we identified cheek teeth and shoulder girdle character complexes as having a high potential to introduce phylogenetic error.“
“We showed that incongruence among mandibulodental, cranial, and postcranial anatomical partitions for the placement of the australosphenidans, haramiyids, and multituberculates could largely be explained by apparently non-phylogenetic covariance from cheek teeth and shoulder girdle characters.”
Based on results recovered in the LRT,
I encourage Célik and Phillips to rerun their analysis with a far larger taxon list. A gradual accumulation of derived traits that mirrors evolutionary events will appear whenever taxon exclusion is minimized.
Célik MA and Phillips MJ 2020. Conflict Resolution for Mesozoic Mammals: Reconciling Phylogenetic Incongruence Among Anatomical Regions. Frontiers in Genetics 11: 0651