Pigs and whales? No.

Sometimes when you add a common extant taxon
to the LRT, there can be more here than meets the eye. That was the case with Sus, the extant pig (Fig. 1).

Figure 1. Skeleton of Sus, the pig, a taxon commonly used as an outgroup for whales. In the LRT it is a sister to other even-toed ungulates, like Giraffa, not Odontoceti nor Mysticeti.

Figure 1. Skeleton of Sus, the pig, a taxon commonly used as an outgroup for whales. In the LRT it is a sister to other even-toed ungulates, like Giraffa, not Odontoceti nor Mysticeti.

Backstory
I was looking at a list of outgroup taxa for whales in Bianucci and Gingerich 2011 and comparing to to the outgroup taxa for whales in Geisler et al. 2011 and other workers:

  1. Gingerich 2011 listed: Elomeryx and illustrated a cow (Bos).
  2. Bianucci and Gingerich 2011 listed: Sinonyx, Mesonyx, Hippopotamus and Sus in that order toward Cetacea.
  3. Geisler et al. listed: Sus, Bos and Hippopotamidae in that order toward Cetacea.
  4. O’Leary and Gatesy 2008 listed: Eoconodon, Sinonyx and Hapalodectes [all considered Mesonychia by them]
  5. O’Leary et al. 2013 listed: Sus, Bos and Hippopotamus in that order toward Cetacea.

Note that
Sus, the pig; Bos, the cow; and Hippopotamus, the obvious, somehow makes it to three lists as outgroup taxa for whales in general. Believe it or not, these three earned their status after testing by traditional paleontologists. Despite having very few traits in common with whales, creating a great leap of phylogenetic faith to connect them all. If you’re bothered by that, I join you!

Figure 1. Ancodus nests as a more derived sister to Sus and it retains digit 1 on the manus and pes.

Figure 2. Ancodus nests as a more derived sister to Sus and it retains digit 1 on the manus and pes. Is this the same taxon as Elomeryx? If not, they appear to be quite close.

Sidenote:
Elomeryx (see above) is said to be widespread and common, but apparently has been confused online with Ancodus (Fig. 1). Are they the same? If different, how different? I’m confused and could use some clarity.

When we add Sus to the LRT
Sus nests much more reasonably between Tapirus and Ancodus (Fig. 2), two pig-like taxa with hooves. Notably extant Sus (Fig. 2) loses digit 1 on both the manus and pes while extinct Ancodus retains those digits indicating a convergent loss of these digits in the ancestors of pigs and in the ancestors of deer + giraffes.

By contrast O’Leary and Gatesy 2008 report, 
“Cetacea was the extant sister taxon of Hippopotamidae, followed successively by Ruminantia, Suina and Camelidae. The wholly extinct Mesonychia was more closely related to Cetacea than was any ‘‘artiodactylan. The osteological–dental data alone, however, did not support inclusion of cetaceans within crown ‘‘Artiodactyla.’ Recently discovered ankle bones from fossil whales reinforced the monophyly of Cetartiodactyla but provided no particular evidence of derived similarities between hippopotamids and fossil cetaceans that were not shared with other ‘‘artiodactylans’’. Can you sense their lack of resolution? Based on present evidence, O’Leary and Gatesy were suffering from taxon exclusion.

No such problem
with the LRT where whales are not related to pigs, cows or camels. Odontocete whales arise from tenrecs. Mysticete whales arise from desmostylians, as we learned earlier here.

References
Bianucci G and Gingerich PD 2011. Aegyptocetus tarfa, n. gen. et sp. (Mammalia, Cetacea), from the middle Eocene of Egypt: clinorhynchy, olfaction, and hearing in a protocetid whale. Journal of Vertebrate Paleontology. 31 (6): 1173–88.
Demere TA, McGowen MR, Berta A & Gatesy J. 2008.
 Morphological and Molecular Evidence for a Stepwise Evolutionary Transition from Teeth to Baleen in Mysticete Whales, Systematic Biology, 57 (1) 15-37. DOI: 10.1080/10635150701884632\
Geisler JH, McGowen MR, Yang G and Gatesy J 2011. A supermatrix analysis of genomic, morphological, and paleontological data from crown Cetacea. Evolutionary Biology 11:112.
Gingerich PD 2005. Aquatic Adaptation and Swimming Mode Inferred from Skeletal Proportions in the Miocene Desmostylian Desmostylus. Journal of Mammalian Evolution, Vol. 12, Nos. 1/2, June 2005.
Gingerich PD 2011. Evolution of whales from land to sea. online here.
Marx FG and Fordyce RE 2015. Baleen boom and bust: a synthesis of mysticete phylogeny, diversity and disparity, Royal Society open Science 2:14034.
Marx FG, Hocking DP, Park T, Ziegler T, Evans AR and Fitzgerald EMG 2016. Suction feeding preceded filtering in baleen whale evolution. Memoirs of Museum Victoria 75:71-82.
O’Leary et al. 2013 The Placental Mammal Ancestor and the Post–K-Pg Radiation of Placentals. Science 339. 662 SuppData.
O’Leary MA and Gatesy J 2008. Impact of increased character sampling on the phylogeny of Cetartiodactyla (Mammalia): combined analysis including fossils. Cladistics 24:397-442.

 

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