masses talk of the first mammals scuttling around at the groundwork of gargantuan dinosaurs but we seldom get as real an illustration as a mammalian skull being found beneath the groundwork bones of a giant dinosaur . No doubt the tremendous skeleton will expatiate our understanding of dinosaur organic evolution , but it is the low skull beneath that could rewrite our theories on both the spread of mammals and movement of continents .
The bones do from a 124 - 139 - million - yr - onetime stratum in Utah , exactly the sort of shoes you ’d carry to find dinosaur remains . SoDr Adam Huttenlockerof the University of Southern California , lead author of a paper inNatureon the discovery , was much more surprised to conclude the small skull accompany the dinosaur bones belonged to a haramiyidan .
Some palaeontologists think these cony - sized creatures reckon as former mammals , while others consider them transitional between reptile and mammals . The skull is from a hahnodontidid and is so exceptionally preserve it confirm the theory , described in the paper as antecedently “ tenuous ” , that the hahnodontidids were a subgroup of harmiyidans .
Early harmiyidan fossils have been find in what is now Europe and Asia . A North American discovery indicates migration between the two continent was still potential around 130 million year ago . It had been thought the break - up of the supercontinent Pangaea had made such a journey unimaginable .
A exclusive find might not be so convincing – it could be a legacy of Hahnodontidae evolving earlier than we cerebrate and a migration while Pangea was still together . " But it ’s not just this group of haramiyidans , " Huttenlocker said in astatement . " The joining we give away mirrors others recognize as recently as this twelvemonth based on standardised Cretaceous dinosaur fossil found in Africa and Europe . "
Huttenlocker and co - authors cite the fossilCifelliodon wahkarmoosuch , the genus name after palaeontologist Richard Cifelli and the species meaning " yellow-bellied true cat " in the Ute lyric of the area ’s first people .
Although we have many tooth and even jaw from Cretaceous mammals in this region of westerly North America , an intact skull is a more exciting find , even aside from the surprising family unit from which it appears to amount . Cifelliodonwas small by today ’s criterion , let alone those of the dinosaur it evaded , but magnanimous compare to the other known mammalian of the area , which were mostly unaired in size to mice and shrews .
“ Even before the raise of mod mammalian , ancient congener of mammals were exploring specialty niches : insectivores , herbivores , carnivores , swimmer , gliders . Basically , they were occupying a diverseness of niche that we see them take today , " Huttenlocker said .
Cifelliodonhad minuscule eyes and tremendous olfactory bulbs , consistent with being nocturnal and surviving mostly on its sense of tone . Its teeth resembled those of modern fruit - eating cricket bat .
