Now that a wide gamut of mammals
has been added to the large reptile tree (LRT, subset Fig. 1), the tree topology has become distinct from prior studies, many of which depend on DNA, which does well in many cases, but makes untenable sisters of several genera.
Case in point: Macroscelidea
(elephant shrews, Fig. 2). Stanhope et al. (1998) proposed the clade Afrotheria based on molecular evidence. Their clade members included elephants and elephant shrews. That’s difficult to accept on the face of it, and the large reptile tree does not recover that relationship.
the large reptile tree recovers:
- Monotremata (Ornthorhynchus) as the most basal mammal clade.
- Didelphis (opossum) is basal to both Metatheria (so far only three genera) and Eutheria.
- The first eutherian split occurs between small carnivores and smaller insectivores
- Carnivora also splits into small insectivores: Chiroptera + (Dermoptera + Primates, including Manis)
- The two tree shrews, Tupaia and Ptilocercus, are not sister taxa.
- The former clade Insectivora is resurrected. It includes Tupaia + elephant shrews, Trogosus + Apatemys and Glires.
- Glires includes the traditional rabbits and rodents, but also shrews, moles and multituberculates
- Condylartha is resurrected and includes ungulates, xenarthrans and paenugulates.
- Maelestes gives rise to tenrecs, which give rise to giant tenrecs and whales.
- Onychodectes + (Pantolambda + Ectoconus) give rise to Xenarthra (sloths, anteaters), Paenungulata (elephants and kin) and Ungulata (hoover mammals).
Not only do these relationships make more sense
on their face, they provide a gradual accumulation of derived characters down to the toes. You can’t do that with ‘Afrotheria’ and other odd-bedfellow sisters that have become widely accepted within paleontology, despite the fact that they make no sense at several nodes. At other nodes, some DNA clades do match morph studies.
we need to look at the results, put our thinking caps on, and toss out DNA results that do not make sense and cannot be supported with morphological studies.
Don’t take my word for it.
I’m reporting results, like Galieo looking through a telescope for the first time or dropping balls off the leaning tower of Pisa. Because this is Science, you can repeat the experiment and discover the mammal family tree for yourself. If you do, let us all know what you recover.
Stanhope MJ, Waddell VG, Madsen O, de Jong W, Hedges SB. Cleven GC, Kao D and Springer MS 1998. Molecular evidence for multiple origins of Insectivora and for a new order of endemic African insectivore mammals. Proceedings of the National Academy of Sciences 95 (17): 9967–9972. Bibcode:1998PNAS…95.9967S. doi:10.1073/pnas.95.17.9967. PMC 21445. PMID 9707584.