Good tidings and well-wishes!
(NOTE #1: Despite WordPress’ argument to the contrary, this post was in fact written on Saturday, January 23rd, so it counts!)
(NOTE #2: Due to the unfortunate fact that I’ve been unable to locate any reconstructions of Prodeinotherium, all of the images displayed in this post depict it’s more famous relative Deinotherium unless otherwise indicated)
As amusement park caricaturists are well-aware, celebrities often become synonymous with a given trait. For instance, if you’re anything like me, when you consider “big chins”, Jay Leno comes to mind, and when someone gives mention to “greasepaint moustaches”, your mind turns to Groucho Marx. In fact, the latter example became so fundamental to the man’s identity that, according to legend, he’d routinely go without his trademark nasal attire to avoid public detection.
This trend isn’t at all unlike that which accompanies how our brain learns to recognize various animals. Attempting to imagine a horse without its hooves or a bird without its feathers often proves to be an extraordinarily difficult feat. Yet, the fossil record clearly indicates that such creatures once existed. In addition, it would appear that, even during their presence, both characteristics have displayed a significant amount of diversity within their respective group’s evolutionary tree. Which brings us to elephants…
Proboscidean trunks, so characteristic of the order’s modern representatives, have likely undergone a similar amount of variety during their 35-million-year-old history, yet it’s notoriously difficult to be more specific to this end due to the fact that they simply don’t fossilize. Thus, with the obvious exception of frozen Mammuthus primigenius specimens, any attempt to reconstruct their appearance on extinct genera must be made on the basis of the skull in question. Yet this is hardly a foolproof method. For instance, most illustrations of Platybelodon, Amebelodon, and their kin display a short, flap-like proboscis which came to be unchallenged within the paleontological community’s collective psyche until Dave Lambert made the assertion that, on the basis of morphological evidence, the trunks of these animals were much more like those of modern elephants. However, when it comes to controversial trunks, no group can challenge the family of this week’s featured beast, the Deinotheriidae.
According to Jeheskel Shoshani and Pascal Tassy’s definitive text “The Proboscidea: Evolution And Paleoecology Of Elephants And Their Relatives”, no one was quite sure what to make of the Deinotheriidae in the years following its discovery in the form of isolated teeth which were assigned to extinct rhinos, tapirs, and ground sloths before “a partial skeleton was unearthed during the collapse of an embarkment on the Prague-Brunn railroad in 1853”. Even now, their taxonomic allegiances remain a point of dispute: though most authorities place them within the proboscidea, others maintain that they represent a sister group.
While their direct ancestry is fairly ambiguous, the earliest Deinothere known to science is the hippo-sized Chilgatherium harrisi from the late Oligocene of Ethiopia, which is consistent with the theory that the proboscidea initially emerged in Africa. The group appears to have persisted for 20 million years until the latest-known genus, Deinotherium bozasi of Kenya, finally went extinct in the late Pleistocene (their extinction may have been directly related to the spread of grasslands and competition from the Elephantids during the Pliocene). During the course of the family’s evolution, relatively few significant anatomical alterations were obtained (especially when one considers the uncanny diversity of the Gomphotheriidae) other than a progressive increase in size. Geographically, the Deinotheriidae was more ‘adventurous’, having spread to Eurasia during the early Miocene with Prodeinotherium sp. leading the charge.
The earliest Prodeinotherium species, P. hobleyi, is known from early Miocene deposits in Eastern Africa. As the genus spread, new species began to appear in Pakistan (P. pentapotamiae) and France (P. bavaricum). During the mid-Miocene, these animals started to become replaced by Deinotherium species: D. bozasi, D. giganteum, and D. indicus, respectively. This raises an intriguing question: did Deinotherium emerge from one ancestral species, or did each aforementioned Deinotherium species evolve from its local Prodeinotherium counterpart? Hopefully, further research will clear up the genus’ mysterious origins.
In “Evolving Eden: An Illustrated Guide To The Evolution Of The African Large-Mammal Fauna”, Alan Turner lists the following characteristics of the Deinotheriidae family:
“Members… have high crested teeth… They are well known in the African fossil record, especially in the Pliocene of eastern areas with the species Deinotherium bozasi… Deinotheres are distinguished from other proboscideans by the absence of upper tusks and the presence of distinctive, downwardly curved tusks in the lower jaw and by the elongated shape of the skull.”
Prodeinotherium is distinguished from its more famous namesake by it’s proportionally smaller size, forelimbs, and molars.
Right, then. Now that we’ve discussed the evolution and distinguishing characteristics of this week’s animal and the family to which it belonged, it’s time for the fun part: analyzing it’s dietary behavior and soft-tissue anatomy (that sentence alone seems sufficient enough to qualify yours truly as a grade-A nerd, but who’s complaining?).
One of the first things any budding paleo-mammology enthusiast grows to learn and appreciate is the importance of mammalian teeth: a fact which is just as prominent in the Deinotheriidae as in any family of mammals. Shoshani writes:
“The… shearing teeth of deinotheres were ideally suited for processing soft foliage. Loss of the upper tusks and the downturned nature of the lower tusks would have permitted more direct access of food to the mouth, and could justify an interpretation of a short, tapir-like proboscis in these animals [(more on that later)]. Many deinothere tusks show evidence of wear, although no consistent wear pattern or location has been identified. The fact that deinotheres had long legs but short necks enables one to argue against frequent use of their tusks for, and [it’s been suggested] that these tusks could have been used as sources of purchase for manipulation of a short proboscis or even for recognition of individuals by members of the same species.”
In “Mammoths, Sabertooths, And Hominids: 65 Million Years Of Mammalian Evolution In Europe” Jordi Agusti makes the following observation:
“The shape of muscle insertion areas in the neck vertebrae and posterior skull of deinotheres reflects a marked specialization for enhanced movement in the vertical plane. Compared with those of a modern elephant, the muscles that pull the head up and those that bring it down [could] act through a wider arc. This was very likely related to the action of the downward-pointing tusks, although the precise function of the tusks remains a matter of debate. Since the deinotheres were clearly obligate browsers- as indicated by the morphology of their cheek teeth- it seems likely that the tusks were used in concert with the trunk to gather foliage from the branches of trees.”
As I hinted at the onset of this post, the trunks of the Deinotheriidae are by a wide margin the family’s most controversial feature. To explain why, allow me to reference an excellent 2008 post on the subject from “The World We Don’t Live In“:
“When [the legendary paleontologist Henry Fairfeld] Osborn first reconstructed Deinotherium back in 1910, he drew it with a short, flap-like trunk much like a tapir’s, but later dropped that reconstruction for no known reason…This reconstruction was revived by [Georgi] Markov [along with his colleagues N. Spassov & V. Simeonovski in 2001] . From a study of the skull’s shape, they deduced that Deinotherium must have had a short, tapir-like snout hanging over its descending lower jaw. A long trunk was not necessary, as a browser standing 5 m high at the shoulder had little need to reach the ground. The tusks remained free for whatever purpose they served, and the nostrils, at the end of the proboscis, could smell and inspect food.”
However, not everyone buys into this interpretation, as many paleo-artists still reconstruct Prodeinotherium and its kin with lengthy, sinuous trunks which resemble those of their modern relatives. Nevertheless, it goes to reveal that, as with a great many congregations of organisms, the scientific community still has much to learn about the evolution and diversity of the proboscidea.
May the fossil record continue to enchant us all!
UPDATE: God, I love my readers! Doug has courteously scanned a few of Mauricio Anton’s amazing Prodeinotherium illustrations which I’ve displayed below (note that the latter sketch compares a P. hobleyi to a modern African bush elephant (Loxodonta africana). Many thanks!!