Seals, sea lions and a ‘possible parallel evolution’ according to Patterson et al. 2020

Patterson et al. 2020 combine
morphological and molecular datasets to find, “many traits shared between extant pinnipeds have arisen independently in the three [extant] clades. Thus, while the present
analysis identifies a new suite of morphological synapomorphies for Pinnipedia, the
frequency of reversals and other homoplasies within the clade limit their diagnostic value.”

The three traditional clades of Pinnipeds
comprise the extant families Odobenidae (the walrus), Otariidae (the eared seals: sea lions and fur seals), and Phocidae (the earless seals, or true seals).

Unfortunately,
taxon exclusion mars Patterson et al. Simply by adding taxa, as in the large reptile tree (LRT, 1882+ taxa; subset Fig. 1) the Pinnipedia is not a monophyletic clade (Fig. 1). The LRT does find parallel evolution in seals + walruses and sea lions, but their last common ancestor is not a ‘pinniped’. Rather their last common ancestor in the LRT was close to Mustela, the European mink.

Enhydra, the sea otter, was included
in the Patterson et al. cladogram using molecular data, but it nested as a taxon with no descendants.

Unfortunately
the wolf, Canis lupus, was specified (= chosen) as the outgroup. In the LRT (Fig. 1) Canis is not basal to seals, sea lions, walruses or even minks. Rather, Canis is a highly derived taxon in the LRT. So, that’s another problem. It would have been better if Patterson et al. had chosen the raccoon, mongoose, kinkajou or coatimundi, even the panda, all basal members of Carnivora, for their outgroup.

Sea lion ancestors in the LRT,
Miacis and Hyopsodus were omitted from the Patterson et al. study.

Seal ancestors in the LRT,
Megistotherium and Palaeosinopa, were also omitted from the Patterson et al. study.

Patterson et al. report
“The Pinnipedimorpha was erected by Berta (1991) and includes Enaliarctos and all of its descendants, including a monophyletic crown-group Pinnipedia, which is strongly supported in all phylogenetic analyses performed in the present study.”

Here in the LRT
the Pinnipeda was shown to be not monophyletic back in 2017. So you heard it here first. If someone suggested this hypothesis of interrelatioships earlier, please provide that citation so I can promote it here. Add taxa to your Carnivora study to confirm or refute the present hypothesis of interrelationships.

References
Paterson RS, Rybczynski N, Kohno N and Maddin HC 2020. A Total Evidence Phylogenetic Analysis of Pinniped Phylogeny and the Possibility of Parallel Evolution Within a Monophyletic Framework. Front. Ecol. Evol. 7:457. doi: 10.3389/fevo.2019.00457

wiki/Pinniped