Hadrosauroid population densities (free pdf)

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Ben Creisler

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Jul 3, 2025, 12:35:45 AM7/3/25
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Ben Creisler


A new paper:

Free pdf:

Jiménez-Moreno Francisco Javier, Ángel Alejandro Ramírez-Velasco, Patricio Ocampo-Cornejo, Jorge Velázquez-Castro & Rodolfo Palomino-Merino (2025)
First Population Analysis in Hadrosauroid dinosaurs (Ornithopoda: Iguanodontia: Hadrosauroidea)
Evolving Earth 100072
doi: https://doi.org/10.1016/j.eve.2025.100072
https://www.sciencedirect.com/science/article/pii/S2950117225000160


Highlights

Mathematical modeling is a powerful tool for inferring population dynamics of extinct fauna.
Ecological analogs can be used to parametrize mathematical models.
Hadrosauroids population densities could have an oscillating period before stabilizing.
The coexistence of diverse species of Hadrosauroids shows high interactive complexity, where periodical seasonal movements and stratigraphic differences played important roles.

Abstract

The study of biological population densities through direct measurements is one of the pillars of modern ecology; however, it does not apply to extinct fauna without modern extant representatives, as is the case with non-avian, plant-eating dinosaurs such as the Hadrosauroidea. On the other hand, mathematical models of population dynamics have also been used to estimate population density without the need for direct measurements. These models, however, require knowledge of population shift rates that are typically obtained through diverse observations. This presents a certain limitation for the use of such models when applied to extinct populations. Still, through the use of ecological analogies, it is possible to estimate population dynamics in extinct faunas. This work, utilizing a differential equation-based population dynamics model, estimates the population density of six species and two specimens of hadrosauroids recorded in Mexican territory, employing ungulate mammals as ecological analogues. The results show that individuals with low body mass, such as Huehuecanahutlus tiquichensis, had a higher average density of 0,69 individuals per square kilometer. For hadrosauroids with higher body mass, such as Magnapaulia laticaudus and the specimen PASAC-1, their population density would be around 0.13 to 0.17 individuals per square kilometer. The inference shows the possible existence of temporal shifts in population density. Maximum and minimum ranges were found due to scenarios of high food productivity or alimentary stress. The former infers a negative correlation between a higher body mass/lesser population density.

Gregory Paul

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Jul 4, 2025, 8:05:49 AM7/4/25
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Here is a funny thing from the Bloody Mary team that tells us that the all the TT-zone lithe tyrannosaurs hypothesis is about to get a great big Type-93 torpedo put into its sinking hull. 

While working on the paper I was of course going to include the specimen # of BM now that it is in the NCMNS collections. So rather than bother anyone I looked at their online catalog. 

Nothing.

Nor for the Triceratops.

Well OK they hadn't gotten around to listing it so I contacted the collections manager. 

Nope, they don't have specimen #s years after their being at the museum. 

Odd, very odd. So why is that? 

When they first got the daring duo the museum was putting out the popular attractions line that they now had a juvenile Trex, albeit acknowledging the possibility it was something else. 

They have dropped that as I have noted in a prior message, just referring to BM as a tyrannosaur in the same sentence they call its (maybe) hapless victim Triceratops. 

One suspects those long, long hands have something to do with that. 

Having a good idea the BM is not a Tyrannosaurus, they are keeping the option of naming the fossil themselves, as they should. 

In order to prevent others from trying to preempt them in the technical literature with a Genus species name, well no specimen number to cite as a holotype, no ability to do that. Clever. 

If it is named it will not be a Nanotyrannus, skull far too different. Maybe a Stygivenator, but as i note in the paper there are problems with that too, including stratigraphic. 

While I am at it, after the Nick & Evans paper came out, Carr in a news article (https://www.livescience.com/animals/dinosaurs/nanotyrannus-vs-t-rex-saga-continues-controversial-study-doesnt-settle-the-question-at-all) said that the two did not understand that there are lots and lots of differences between juv and adult Tyranno. After all, he found over 1800 of them in his 2020 paper, so it is not appropriate to cite the differences as evidence they are not the same species. Ummm, that is not the parsimonious null hypothesis. That is pure circular reasoning. The reason there are so many diffs between most of the TT-zone little ones is because they are not the same species. 

Why am I the one that has to explain all this? 

GSPaul


Jacqueline Silviria

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Jul 4, 2025, 10:56:57 AM7/4/25
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Greg, you’re reading way too much into this. Since the BM specimens are still under prep as of May 2025 (L. Zanno, pers. comm.), they likely haven’t yet been given accession numbers (that is, numbers for final storage, not field jacket numbers) and/or they haven’t been added to the NCMNS online catalog. Hence the comment you received from their collections manager.

It is alarming but not uncommon for specimens to not receive numbers years after storage, or for there to be discrepancies between the official total number of ascension numbers and what’s reported in publicly available digital catalogs. To give a few examples:

I recently visited AMNH Fossil Mammals to study, among other samples, the Bug Creek Anthills and Lance Creek concentrates in the McKenna collection, screen-washed in the early 1960s. Almost all of the ~790 identified Bug Creek mammal specimens have been given accession numbers, but had not been updated in either version of the AMNH online catalog. That included two specimens I’ve since loaned for micro-CT scanning, which had to be updated in the system by the collections managers. 

At the Burke Museum where I work, there was until very recently an enormous backlog of sorted but unnumbered specimens in the Hell Creek Project collection going as far back as 2009. Adding those to both our in-house database and to Arctos required a massive combined effort from myself and other grad students, our undergraduate work-study students volunteers, and our postundergraduate and postgraduate research associates. Also, it is not uncommon for the Burke “dino crew” in the prep lab to not provide accession numbers to specimens prior to completion of preparation and identification (unless requested by a curator or lab manager), although an accessioned specimen may be sent back if more work is needed or if needs to be repaired after an accident.

No need to entertain conspiracies about taxon naming rights.

Jacqueline S. Silviria
she/her/hers
The Last King of the Jungle

Department of Earth & Space Science
University of Washington
Seattle, WA, USA
jsi...@uw.edu, sympan...@gmail.com


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Gregory Paul

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Jul 4, 2025, 1:21:36 PM7/4/25
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Maybe. But whether a specimen is prepped or not usually is not important to it being accessioned, there are museums full of such dating back decades that have numbers for basic management purposes. And these are just two, very major specimens. And there is a real risk of someone naming BM if there is a catalog number out there, so it would be a smart move on their part. I know they don't have numbers because I asked the collections manager. 

As for how long prep will take, could be a good while because they are in hard sandstone. 

GSPaul

Jerry Harris

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Jul 4, 2025, 1:49:57 PM7/4/25
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Well, AFAIK, all specimens come into museums from the field with field numbers, which are not the same as catalog numbers—they're just there to match up specimens, jackets, etc. with field notes. Field numbers don't ever really go away; it gets tied to an accession number, which exists to demonstrate that a specimen, jacket, etc. now resides in a museum. (Depending on the field numbering system used, field numbers can be identical to accession numbers.) Once a specimen is prepped and ready to become part of the permanent collection, it's then given a collections (specimen) number, which subordinates, but does not delete, the field and accession numbers. The field and accession numbers are linked to the collections number to preserve the connection to field notes and the progress of the specimen(s) through the system. Field and accession numbers can't, as a matter of principle, always be tied to a single individual taxon or bone because an incoming field jacket might contain elements from multiple individuals and/or species—accession numbers very often are given to incoming "lots"—each of which has to be teased out during preparation and can then be given discreet specimen numbers. I'm sure the "dueling" specimen at NC has an accession number at the very least, but that won't satisfy the ICZN rules. Whether the two animals contained in the block are ultimately given variations of the same specimen number (something like "NC5000A" and "NC5000B") or completely discreet numbers will be, I guess, up to the collections manager there. I think it's good practice in general to not assign permanent collection numbers until the nature of a specific specimen is entirely known, which requires complete prep, which, as Greg noted, in this case is probably going to take some time because of the nature of the matrix. (Assuming the sandstone is hardened by calcite cement, I often wonder about the utility of acid prep in a swimming pool...)

Jacqueline Silviria

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Jul 4, 2025, 3:15:50 PM7/4/25
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Thank you for your service, Jerry. I thought Greg would know better than to confuse field numbers and accession numbers, given his fieldwork in the 70s-80s and his decades of experience within the community. Memory does fade with age, it’s true, but still...

Jacqueline S. Silviria
she/her/hers
The Last King of the Jungle

Department of Earth & Space Science
University of Washington
Seattle, WA, USA
jsi...@uw.edu, sympan...@gmail.com

Gregory Paul

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Jul 4, 2025, 3:52:10 PM7/4/25
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What, you are committing age bigotry? Excuse me? 

And of course I know the difference between field and museum numbers. Jeez. 

Museum catalog numbers have not been applied to two major, well articulated specimens years after being acquired by a museum. It remains strange.

GSPaul

Jura

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Jul 4, 2025, 4:59:57 PM7/4/25
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I was finishing up my postdoc when the museum first acquired the specimens. At the time it was mostly a "handshake" deal as Lyndsey was still working with the museum to raise enough money to cover BHI's hefty price tag for the two fossils. This lasted for three or four years before the fossils could finally be paid for and the museum could officially announce that they had it. For all that time the specimens just sat in storage with no one allowed to take pictures or work on them. Throw in one pandemic to further slow things down and finally toss in another year or so on the major renovations to the space where they are now housed (which means they are still just sitting there) and it's less surprising that these specimens don't have an official accession number. I suspect that should change within the next year as they finally start getting prepped out. 

Jason

Ethan Schoales

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Jul 4, 2025, 5:01:23 PM7/4/25
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What does ETRH stand for?

The Dinosaur Heretic

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Jul 4, 2025, 5:02:12 PM7/4/25
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“Everything is Tyrannosaurus rex Hypothesis”, apparently.

Ethan Schoales

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Jul 4, 2025, 5:02:48 PM7/4/25
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Are you Robert Bakker?

The Dinosaur Heretic

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Jul 4, 2025, 5:03:41 PM7/4/25
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Hahaha, no, I just really love the book.

Gregory Paul

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Jul 4, 2025, 5:15:21 PM7/4/25
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Everything is Tyrannosaurus rex hypothesis. As per what Carr, Brusatte and so on are proposing. 

It is in the Mesozoic paper. 

Along with some other annoying but what are you going to do abbreviations. 

A reviewer was not happy with them. But also acknowledged spelling them out all the time would be about as bad. I set up a brief list in the Methods section and left it up to the editor what to do with them and they stayed. 

GSPaul

Gregory Paul

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Jul 4, 2025, 5:18:49 PM7/4/25
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Dr Bob never uses the public internet. Not sure how active he is these days, he is 80. 

Once saw his birth certificate lying in the lab at Hopkins when he was 35. Long ago. 

GSPaul

Mickey Mortimer

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Jul 7, 2025, 9:15:49 AM7/7/25
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I should also note a specimen number is not necessary to erect a new species under the ICZN. It's just a recommendation- e.g. "Recommendation 16D. Publication of information distinguishing type specimens. When providing information to distinguish the type specimen(s) from other specimens (Article 16.4.1) authors should include information such as specimen numbers and descriptions of labels", "Recommendation 73C. Data on the holotype. An author who establishes a new nominal species-group taxon should publish at least the following data concerning the holotype, if they are relevant and known to the author: ... 73C.6. the collection in which it is situated and any collection number or register number assigned to it;". So anyone could just try to name Jane or Bloody Mary or whatever, but like Ajancingenia I doubt the community would stand for it if it wasn't done ethically.

Having been researching the Bissekty theropod specimens at the ZIN lately, it looks like the vast majority of dinosaur specimens were left uncatalogued since their discovery which started in the 1970s, then in the 2000s somebody finally went through them and e.g. tried to pick our all the ornithomimosaur caudals and give them sequential numbers. Museums aren't exactly packed with funds or people to do the work of cataloging.

Mickey Mortimer

Gregory Paul

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Jul 7, 2025, 9:31:12 AM7/7/25
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And the Tendaguru material was named without museum #s, it was field numbers. That was back in the day. If someone slipped a name for BM in the peer reviewed literature I don't know if anyone could do anything about it. 

GSPaul

Skye McDavid

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Jul 7, 2025, 9:33:39 AM7/7/25
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Confirming what everyone else has said about something not being accessioned doesn't mean anything. 

I recently went to a major US museum which had material purchased from "C. Sternberg" (I assume Charles Hazelius given Charles Mortram would have been in his teens at the time) in 1899 that still had not been accessioned and given a number, but they were able to give it a number while I was there. 

When I visited NCMNS (as a visitor only) in November of 2024, Bloody Mary and Trike were actively being prepped. BM does have beautifully preserved articulated gastralia. 

Indeed, the catalog number isn't necessary, and was often omitted until the 20th century. For a recent-ish case, Nevadadromeus was named with a field number and a note that it was going to be accessioned into the collections of Nevada State Parks. 

To view this discussion visit https://groups.google.com/d/msgid/DinosaurMailingGroup/aa3937a9-2613-47d3-bff8-5b5ced8cf169n%40googlegroups.com.


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