Deinotherium enters the LRT with Gomphotherium

Known since Kaup 1829,
Deinotherium giganteum (Kaup 1829; Late Miocene; Figs 1, 2) is a large deinothere (Fig 2), the clade of elephants lacking premaxillary tusks. Instead large dentary (= mandible) tusks curl ventrally then posteriorly in all deinotheres (Fig 2) , distinct from all other elephant genera, as everyone already knows. Interrelationships have been traditionally murky since transitional taxa have not yet been documented.

Figure 1. Skull of Deinotherium in two views. Colors added here. Note the enormous naris visible in dorsal view. The nasals are either absent or fused to the frontals in this diagram.

Here
in the large reptile tree (LRT, 2061 taxa) Deinotherium (Fig 1) nests with Gomphotherium (Figs 3, 4), another tested taxon with large dentary tusks. Both arise from small pre-elephant taxa, like Notostylops (a pre-manatee) and Procavia, the extant hyrax.

Figure 2. Deinotherium figures from Larramendi 2016.

Larramendi 2016
published several excellent lateral view skeletons of deinotheres (Fig 2) and gomphotheres (Fig 3) along with several other elephant clades.

Larramendi 2016 calculated body mass in extinct taxa
“by the by the Graphic Double Integration volumetric method which is based on technical restorations from graphical reconstructions of fossils employing photos, measurements and comparative anatomy of extant forms. The method has been tested on extant elephants with highly accurate results. From the shoulder heights, several equations were created to find out the body mass of a series of extant and extinct species. A few of the largest proboscideans, namely Mammut borsoni and Palaeoloxodon namadicus, were found out to have reached and surpassed the body size of the largest indricotheres.”

In the LRT (Fig 5) indricotheres are giant three-toed horses.
Horses and rhinos are hyracodontids.
Those are tapir relatives.
Those are chalicothere and hyrax relatives.
Those are Ectocion relatives.
Those are artiodactyl relatives.
Those are oreodont and mesonychid relatives.
Etc.

Figure 3. Gomphotherium, like Deinotherium, had a longer dentary and dentary tusks.

A recent paper by Baleka et al. 2022
produced a phylogenetic analysis of elephants using total evidence (genes + traits). They wrote: “The order originated around 60 million years (Ma) ago in Africa. At present, the oldest proboscidean fossil is Phosphatherium escuilliei Gheerbrant, Sudre & Cappetta,1996, from Morocco. It comprises cranial and mandibular elements dating to 55 Ma (Gheerbrant,
2009).

We will take a closer look at Phosphatherium from Paleocene Morocco in the near future. Turns out it’s not a direct elephant ancestor (Fig 5) in the LRT.

Baleka et al. 2022 continue:
“The evolutionary history of proboscideans is marked by three major radiations.”

“The first occurred during the late Palaeocene/Eocene, with the diversification of primitive proboscideans.”

“The second radiation took place during the early Miocene, with the diversification of ‘‘Gomphotheriidae’’ Hay, 1922, (used sensu lato throughout the text, indicated by brackets) Mammutidae Hay, 1922, and Stegodontidae Osborn, 1918, a family within the Elephantoidea.”

“The last radiation took place during the late Miocene/early Pliocene and resulted in the diversification of Elephantidae Gray (1821), as well part of the superfamily Elephantoidea, including the living elephants.”

The LRT indicates elephant ancestors do not include Phosphatherium, but arise directly from Procavia-llike and Diadiaphorus-like tusked taxa.

Figure 4. Gomphotherium jaws. Note the elongate dentary and large dentary tusks. Those are not seen in other elephant clades.

Baleka et al. reported,
“The historical biogeography analysis (Figures 4, S4, and S5) suggests that proboscideans may have left Africa only three times in phylogenetically distant clades (Deinotherium or Deinotheriidae, Mammutidae, and Elephantida).”

The LRT nests Elephas with Mammuthus and Deinotherium with Gomphotherium.
Mammut (the mastodon) has not yet been tested.

Figure 5. Subset of the LRT focusing on elephants and their relatives. As in Baleka et al. 2022, Deinotheres are close to Palaeomastodon. Distinct from Bakeka et al. Gomphotherium nests with deinotheres here, rather than closer to extant elephants than Mammut the mammoth. Be wary of DNA studies.

References
Baleka et al. 2022. Revisiting proboscidean phylogeny and evolution through total evidence and palaeogenetic analyses including Notiomastodon ancient DNA. iScience 25, 103559 https://doi.org/10.1016/j.isci.2021.103559
Kaup JJ 1829. Neues Säugethier, Deinotherium: Deinotherium giganteum. Isis 22(4):401–404
Larramendi A 2016. Shoulder height, body mass, and shape of proboscideans. Acta Palaeontologica Polonica 61 (3):537–574.

Proboscidea Illiger 1811
alchetron.com/Deinotherium