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Maastrichtian generic distribution?

I was a little surprised by Mike's numbers. The Late Jurassic numbers were higher than I would have guessed, and even the Late Triassic numbers are very good.
Looks like the dinosaurologists are doing a pretty good job of finding these older dinosaurs (and kin). It certainly seems like Ornithodira established their success relatively quickly, and thenceforth displayed what one might expect----a relatively stable succession of faunas gradually replacing one another throughout the Jurassic and Cretaceous.
Are there any figures on the breakdown of genera (or species) numbers for the Maastrichtian in particular. Is it pretty steady throughout this last period of dinosaur evolution until the sudden extinction at the end?
From: "T. Mike Keesey" <tmk@dinosauricon.com>
Reply-To: tmk@dinosauricon.com
To: ArtSippo@aol.com
CC: dinosaur@usc.edu
Subject: Re: How many genera per era?
Date: Fri, 17 Nov 2000 23:31:52 -0500 (EST)

On Thu, 16 Nov 2000 ArtSippo@aol.com wrote:

> It seems to me that the 850+ known dinosaur genera is a very small number
> considering the fact that dinosaurs were the dominant terrestrial life form
> for 160 million years. I am sure this is due to serendipity in fossil
> preservation.
> Nevertheless, I was wondering how the known genera are distributed over the
> Mesozoic Era. What percentage come from what periods? As time went on, were
> the number of fossilized genera increasing, decreasing, or staying the same?

I did a quick text search through my data files, and tallied number of
times an age is mentioned. Here (with some possible errors -- explained
below) are the numbers of genera (named and unnamed) of non-neornithean
Ornithosuchia (Dinosauria, Pterosauria, "Lagosuchia") from each age of the
Mesozoic Era:

Middle Triassic:
      Anisian         0
      Ladinian        4
Late Triassic:
      Carnian         32
      Norian          28
      Rhaetian        4
Early Jurassic:
      Hettangian      16
      Sinemurian      16
      Pliensbachian   15
      Toarcian        11
Middle Jurassic:
      Aalenian        5
      Bajocian        11
      Bathonian       21
      Callovian       23
Late Jurassic:
      Oxfordian       14
      Kimmeridgian    71
      Tithonian       65
Early Cretaceous:
      Berriasian      8
      Valanginian     19
      Hauterivian     18
      Barremian       73
      Aptian          87
      Albian          102
Late Cretaceous:
      Cenomanian      64
      Turonian        24
      Coniacian       25
      Santonian       27
      Campanian       143
      Maastrichtian   126


-Animals whose age is not known are not included, even if their period or
epoch is. (decrease)

-If an exact age is not known, but the animal is known to belong to one of
two adjacent ages, both ages are included. (increase)

-Sometimes I have entered a single age for a whole genus, sometimes (much
more rarely) I have done it for individual species. (increase)

-Neornithes are excluded. (decrease)

-Indeterminate material, which may belong to already recognized species,
is included. (increase)

-Whenever an age is mentioned in an essay, that is counted. (increase)

Hopefully these balance each other out somewhat, although the numbers are
probably just a little bit high.

Also worthy of note is that not all ages are equal in length. Thus,
although it seems like there were *way* more Ornithodira during the Aptian
(87) than during the Santonian (27), the Aptian was nearly 9 million years
long, whereas the Santonian was a mere 2.3. The Santonian actually has a
*higher* ratio of genera per Mega annum (11.7, as opposed to 9.89 for the

Incidentally, until I get a search engine set up on my site, a good way to
find all entries from a certain age is to use Google's search engine

of Age>



(I hate that they use the dinosaur.umbc.edu URL instead of
dinosauricon.com, but....)

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