Convergent Evolution’s Dinosaur Crested Mammal Rusingoryx atopocranion

Summary: Duck-billed dinosaurs 65 million years ago and Rusingoryx atopocranion 64.9 million years later show convergent evolution’s power in same-use head crests.

Artist's interpretation of Rusingoryx atopocranion on Late Pleistocene plains of what is now Rusinga Island in Kenya's portion of Lake Victoria. Scientists have found links between Rusingoryx and hadrosaur dinosaurs -- especially the large, hollow dome that makes a crest atop animal's skull: Todd S. Marshall (http://www.marshalls-art.com) via EurekAlert!

Duck-billed dinosaurs 65 million years ago and Rusingoryx atopocranion 64.9 million years later show convergent evolution’s power in same-use head crests.

Eleven paleontologists are suggesting that convergent evolution explains the same-look, same-use head crests that appear on duck-billed dinosaurs and Rusingoryx atopocranion, according to a study published in Current Biology Feb. 4, 2016.

One biologist, two archaeologists, two earth scientists, three anthropologists and three geologists base their findings upon acoustical modeling, anatomical observations and computer tomography of six skulls. Five researchers in the United States and six in Australia consider the crests resonance chambers for producing sounds in the way that elephants trumpet through trunks.

Haley O’Brien of Ohio University in Athens describes the low-frequency, 250- to 750-hertz sounds on “the same sonic frequencies of a vuvuzela [South African stadium horn].” She expects that on divergent prehistoric animals convergent evolutionary head crests represent the same responses to similar pressures.

Paleontologists find fossilized hadrosaurs, dinosaurs with flat, toothless, wide mouths, predominantly in North America from Late Cretaceous geological timescales of 80 to 65 million years ago.

Fossilized specimens give evidence of low reptilian heads that oftentimes are crested with a bony protrusion atop the skull in a dome-like or a rod-like shape. Fossils of 15-meter- (49.21-foot-) long, 5-ton Lambeosaurus of Canada, Mexico and the United States have forehead-protruding, hatchet-shaped crests that merge left and right nostril airways into one. They indicate a skin whose pebble-like, small scales are embedded in a leathery hide and whose protective covering of the crest often is interpreted as colorful.

Crests juggle functions of display in courting and recognition in herding, according to David Evans of Canada’s Royal Ontario Museum.

Seventy-five-thousand-year-old fossils of Rusingoryx atopocranion, Late Pleistocene mammal whose closest relatives are curved-horned, heavy-necked, horse-tailed, ox-headed wildebeests of South Africa, keep traces of similar head crests. Twenty-four sets of bones from Kenya’s Bovid Hill site on Rusinga Island in Lake Victoria lack the throat’s soft tissue for reconstructing how crest-resonated frequencies sound.

J. Tyler Faith of the University of Queensland in Brisbane, Australia, mentions excavating butchered bones and stone tools along with the fossilized herd from 2009 onward. He notes that “I was astonished to see that [the skulls] looked unlike any antelope that I had ever seen” since “The anatomy was clearly remarkable.”

Professors Faith and O’Brien opt for vocalizing, over cooling or warming incoming air and thin-skulled crest-butting as functions of crests.

Convergent evolution prompted duck-billed dinosaurs and plant-eating Rusingoryx atopocranion to change cheek bones and lower jaws, to elongate noses and to link respiratory and vocal tracts. The need of sturdy dentition for duck-billed dinosaurs in rainforests and of “tall teeth” for Rusingoryx atopocranion in grasslands qualified as common means, motives and opportunities.

Ali Nabavizadeh of Illinois’ University of Chicago reacts favorably to the study’s suggestions that on divergent prehistoric animals convergent evolutionary head crests produce infrasounds and sounds. He suggests: “Infrasound [inaudible to humans] … is able to travel over great distances and open areas [for Rusingoryx atopocranion] and in closed environments [for hadrosaurs].”

So socialization and terror turn ancient mammals and prehistoric dinosaurs into vocalizers “in stealth mode” or of “low trumpeting” sounds.

Rusinga Island, site of Rusingoryx atopocranion fossil, as viewed from southeast; fossil-rich Rusinga Island lies in Kenya's small portion of Lake Victoria: Küchenkraut, CC BY SA 3.0, via Wikimedia Commons

Acknowledgment

My special thanks to talented artists and photographers/concerned organizations who make their fine images available on the internet.

Image credits:

Rusingoryx atopocranion: Todd S. Marshall (http://www.marshalls-art.com), usage restriction: credit required, via EurekAlert! @ http://www.eurekalert.org/multimedia/pub/107770.php

Rusinga Island: Küchenkraut, CC BY SA 3.0, via Wikimedia Commons @ https://commons.wikimedia.org/wiki/File:Rusinga_Island_-_Lake_Victoria_-_Kenya.jpg

For further information:

Ancient Wildebeest-like Animal Shared ‘Bizarre’ Feature with Dinosaur.” Phys.Org > Other Sciences > Archaeology & Fossils > Feb. 4, 2016.
Available @ http://phys.org/news/2016-02-ancient-wildebeest-like-animal-bizarre-feature.html

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O’Brien, Haley D.; Faith, J. Tyler; Jenkins, Kirsten E.; Peppe, Daniel J.; Plummer, Thomas W.; Jacobs, Zenobia L.; Li, Bo; Joannes-Boyau, Renaud; Price, Gilbert; Feng, Yue-xing; Tryon, Christian A. 22 February 2016. “Unexpected Convergent Evolution of Nasal Domes between Pleistocene Bovids and Cretaceous Hadrosaur Dinosaurs.” Current Biology 26 (4): 1–6. Received Sept. 1, 2015. Received in revised form Nov. 18, 2015. Accepted Dec. 14, 2015. Published Feb. 4, 2016. http://dx.doi.org/10.1016/j.cub.2015.12.050
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