Elephantimorpha is a
clade
In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...
of
proboscideans that contains the
Mammutidae (mastodons), as well as Elephantida (
amebelodonts,
choerolophodonts,
gomphotheres
Gomphotheres are an extinct group of proboscideans related to modern Elephant, elephants. First appearing in Africa during the Oligocene, they dispersed into Eurasia and North America during the Miocene and arrived in South America during the Ple ...
,
stegodontids and
elephantids). All members of Elephantimorpha have the horizontal tooth replacement typical of modern elephants, where the cheek teeth progressively migrate forwards in the jaw like a conveyor belt. This a distinctive characteristic of this group (
synapomorphy
In phylogenetics, an apomorphy (or derived trait) is a novel Phenotypic trait, character or character state that has evolution, evolved from its ancestral form (or Plesiomorphy and symplesiomorphy, plesiomorphy). A synapomorphy is an apomorphy sh ...
) and is not found in more primitive non-elephantimorph
Elephantiformes. Members of Elephantida are distinguished from mammutids by the reduced
angular process of the lower jaw. Like modern elephants, the ancestor of Elephantimorpha was likely capable of communicating via
infrasonic
Infrasound, sometimes referred to as low frequency sound or incorrectly subsonic (subsonic being a descriptor for "less than the speed of sound"), describes sound waves with a frequency below the lower limit of human audibility (generally 20 Hz ...
calls. While early elephantimorphs generally had lower jaws where the fused front part (the
mandibular symphysis
In human anatomy, the facial skeleton of the skull the external surface of the mandible is marked in the median line by a faint ridge, indicating the mandibular symphysis (Latin: ''symphysis menti'') or line of junction where the two lateral ha ...
) was greatly elongated with well developed lower tusks/incisors, from the Late Miocene onwards, many groups convergently developed brevirostrine (shortened) lower jaws with vestigial or no lower tusks,
probably corresponding with the elongation and increasingly dexterity of the trunk allowing it to be used as the primary feeding organ.
The closest relatives of modern elephants within Elephantida, typically including Stegodontidae and the "tetralophodont gomphotheres" are placed as part of the clade Elephantoidea, though this clade has also been used historically as equivalent in scope to Elephantimorpha or Elephantida.
Taxonomy
Cladogram of Elephantiformes after Li et al. 2023, showing a
paraphyletic
Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic ''with respect to'' the excluded subgroups. In co ...
Gomphotheriidae
Gomphotheres are an extinct group of proboscideans related to modern elephants. First appearing in Africa during the Oligocene, they dispersed into Eurasia and North America during the Miocene and arrived in South America during the Pleistocene ...
.
References
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