[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Re: Rantings on Polled Ceratopsians
On Thu, 01 Feb 2001 17:23:03
Matthew Bonnan wrote:
Steve Brusatte said:
"Ceratopsians are often compared to cattle. <snip> However, has
any serious thought been given to the possibility of _Monoclonius_
being a primarily polled species? Polled, in terms of cattle, means
possessing no horns. In many types of cattle, horns are not
dimorphic or necessarily display features. Instead, they are
caused by recessive genes (a series of two autosomal pp genes).
On the other hand, being polled, is dominant (either Pp or PP).
"Could individuals attributed to the genus _Monoclonius_ actually
have been polled members of a species, with polled in this sense
meaning only a single horn, compared to three with _Triceratops_
and other ceratopsian genera? Is there a possibility that
elaborately horned ceratopsians, which are very common, were
possessors of the recessive genes for several horns, such as those
seen in cattle. Or, perhaps, in the ceratopsid lineage, the genes
for horns were dominant (PP)?"
Hi, Steve and all. I've been lurking for a while, doing
paleontological things in the shadows. =) However, I thought I
might add my two cents to this question. As I study sauropods, I
would never claim to be a ceratopsian expert. However, your
suggestion is intriguing about the polling aspect of cattle and its
implications for horns in Monoclonius and other ceratopsians.
Before we look at cattle, it might be instructive to examine
horned reptiles. I am unaware (or at least forgetful) of any
extant archosaurs with horns on the skull, so one might examine
lepidosaurs (lizards, snakes, and the tuatara for those on the list
who might not know) and see if polling or other such things
happen in those lepidosaurs that do develop horns or such on
Yes, I would be interested to know of any living archosaurs, or any reptiles,
for that matter, that have genes for polling.
It is always tempting to look for modern analogs to dinosaurs in
living mammals, but we must be very careful. In the sauropods,
the analogy to elephants has been overextended time and again
for everything from locomotion to behavior in animals that were
quite different from elephants. The same may be happening with
ceratopsians. Yes, they have horns that remind us of present day
cattle, but how far does the analogy go? We must remember,
too, that compared to mammals, so much anatomy and
physiology in reptiles remains poorly known. Most of us who
have taken or teach comparative vert classes have the tendancy
to emphasize mammalian anatomy and physiology as the "norm,"
while short shifting the reptiles. This has led sometimes, IMHO,
to the expectation that the mammalian way of putting the limbs,
verts, etc., together is the "best" or "ideal model" way, whereas
other anatomical plans are sometimes viewed as being aberrant
from those of mam! mals. Walter Coombs (1975, Sauropod
habits and habitats. Palaeogeography, Palaeoclimatology,
Palaeoecology, 17: 1-33) describes the dangers of analogizing
sauropods with elephants in his paper, and if memory isn't failing
me this morning, so does Paul Upchurch (1994, Manus claw
function in sauropod dinosaurs. GAIA, 10: 161-171).
Yes. As I said in my first post, ceratopsians are often compared to cattle,
but this doesn't mean a thing in a genetic or phylogenetic sense. The only
reason I was comparing them to cattle in this instance because cattle are the
only animals in which I am positively sure possess a recessive gene for horns,
and have polling. Of course, I assume that other species also possess this
The polling idea is intriguing, and although not directly testable on
dinosaurs, may have some testability elsewhere in extant reptiles
and mammals. I'd be interested to see what happens with horns
in reptiles, and if there is something like polling.
I, too, am very interested in looking at reptile horns. I am not in a position
to do so, as a student with no access to a university library and a relatively
weak knowledge of cladistics and genetics (although I am definitely making
However, I do think this would be a great project for somebody to take up,
possibly myself at a later date. No, this cannot be tested in dinosaurs
unless, as I said, we can decipher an entire ceratopsian genome (for every
genera/species!!), or we had an extremely large sample, all preserved at the
same location at the same time and only of one species. Even if this were the
case, it would still be very hard to do any genetic work.
I am interested in more input on this idea. Does anyone take seriously the
idea that _Monoclonius_ may be a polled member of a species, and not a juvenile
or individual species??
Dino Land Paleontology
Get your small business started at Lycos Small Business at