Open access article:

Dental form and function in the early feeding diversification of
dinosaurs

Abstract

Dinosaurs evolved a remarkable diversity of dietary adaptations
throughout the Mesozoic, but the origins of different feeding modes
are uncertain, especially the multiple origins of herbivory. Feeding
habits of early dinosaurs have mostly been inferred from qualitative
comparisons of dental morphology with extant analogs. Here, we use
biomechanical and morphometric methods to investigate the dental
morphofunctional diversity of early dinosaurs in comparison with
extant squamates and crocodylians and predict their diets using
machine learning classification models. Early saurischians/theropods
are consistently classified as carnivores. Sauropodomorphs underwent a
dietary shift from faunivory to herbivory, experimenting with diverse
diets during the Triassic and Early Jurassic, and early ornithischians
were likely omnivores. Obligate herbivory was a late evolutionary
innovation in both clades. Carnivory is the most plausible ancestral
diet of dinosaurs, but omnivory is equally likely under certain
phylogenetic scenarios. This early dietary diversity was fundamental
in the rise of dinosaurs to ecological dominance.
https://www.science.org/doi/10.1126/sciadv.abq5201

On Sat, 17 Dec 2022 14:01:31 +0100, Pandora <pandora@knoware.nl>
wrote:

>This early dietary diversity was fundamental
>in the rise of dinosaurs to ecological dominance.
>https://www.science.org/doi/10.1126/sciadv.abq5201

But not by dentition alone.

Open access article:

Climatic controls on the ecological ascendancy of dinosaurs.

Highlights:

*Early diverging sauropodomorphs were characterized by a cooler
climatic niche

*Later in the Early Jurassic, sauropodomorphs shifted to warmer niches

*This shift towards warmer climatic niches occurred during the origin
of the Sauropoda

*The global abundance of sauropodomorph dinosaurs was facilitated by
climatic change

Summary

The ascendancy of dinosaurs to become dominant components of
terrestrial ecosystems was a pivotal event in the history of life, yet
the drivers of their early evolution and biodiversity are poorly
understood. During their early diversification in the Late Triassic,
dinosaurs were initially rare and geographically restricted, only
attaining wider distributions and greater abundance following the
end-Triassic mass extinction event. This pattern is consistent with an
opportunistic expansion model, initiated by the extinction of
co-occurring groups such as aetosaurs, rauisuchians, and therapsids.
However, this pattern could instead be a response to changes in global
climatic distributions through the Triassic to Jurassic transition,
especially given the increasing evidence that climate played a key
role in constraining Triassic dinosaur distributions. Here, we test
this hypothesis and elucidate how climate influenced early dinosaur
distribution by quantitatively examining changes in dinosaur and
tetrapod “climatic niche space” across the Triassic-Jurassic boundary.
Statistical analyses show that Late Triassic sauropodomorph dinosaurs
occupied a more restricted climatic niche space than other tetrapods
and dinosaurs, being excluded from the hottest, low-latitude climate
zones. A subsequent, earliest Jurassic expansion of sauropodomorph
geographic distribution is linked to the expansion of their preferred
climatic conditions. Evolutionary model-fitting analyses provide
evidence for an important evolutionary shift from cooler to warmer
climatic niches during the origin of Sauropoda. These results are
consistent with the hypothesis that global abundance of sauropodomorph
dinosaurs was facilitated by climatic change and provide support for
the key role of climate in the ascendancy of dinosaurs.
<https://www.cell.com/current-biology/fulltext/S0960-9822(22)01894-2>

On 12/17/22 5:01 AM, Pandora wrote:
> Open access article:
>
> Dental form and function in the early feeding diversification of
> dinosaurs
>
> Abstract
>
> Dinosaurs evolved a remarkable diversity of dietary adaptations
> throughout the Mesozoic, but the origins of different feeding modes
> are uncertain, especially the multiple origins of herbivory. Feeding
> habits of early dinosaurs have mostly been inferred from qualitative
> comparisons of dental morphology with extant analogs. Here, we use
> biomechanical and morphometric methods to investigate the dental
> morphofunctional diversity of early dinosaurs in comparison with
> extant squamates and crocodylians and predict their diets using
> machine learning classification models. Early saurischians/theropods
> are consistently classified as carnivores. Sauropodomorphs underwent a
> dietary shift from faunivory to herbivory, experimenting with diverse
> diets during the Triassic and Early Jurassic, and early ornithischians
> were likely omnivores. Obligate herbivory was a late evolutionary
> innovation in both clades. Carnivory is the most plausible ancestral
> diet of dinosaurs, but omnivory is equally likely under certain
> phylogenetic scenarios. This early dietary diversity was fundamental
> in the rise of dinosaurs to ecological dominance.
> https://www.science.org/doi/10.1126/sciadv.abq5201

So basic questions. In modern herbivorous mammals there
are fore gut fermenters that break down cellulose through
the use of bacteria prior to the bacteria being attacked by
hydrochloric acid in a regular stomach or an abomasum. Some
of them use a rumen and some a pseudorumen.

There are also hind gut fermenters that break down cellulose
using bacteria in the intestine after passing through the
acid stomach.

Modern birds have no teeth but there are fossil teeth for
herbivorous dinosaurs.

Many modern birds have a crop - a modified esophagus for
storing food, a proventriculus - an acid stomach, and
then a gizzard - a grinding organ often with gizzard
stones after the acid stomach.

Were there a lot of dinosaurs that were fore gut fermenters,
breaking down cellulose in the crop prior to something like
a proventriculus, or were most hind gut fermenters, generally
using gizzards for fine grinding with cellulose being broken
down likely by bacteria in the intestine or cecum?

On Sun, 18 Dec 2022 04:08:35 -0800, Trolidan7
<Trolidan7@eternal-september.org> wrote:

>On 12/17/22 5:01 AM, Pandora wrote:
>> Open access article:
>>
>> Dental form and function in the early feeding diversification of
>> dinosaurs
>>
>> Abstract
>>
>> Dinosaurs evolved a remarkable diversity of dietary adaptations
>> throughout the Mesozoic, but the origins of different feeding modes
>> are uncertain, especially the multiple origins of herbivory. Feeding
>> habits of early dinosaurs have mostly been inferred from qualitative
>> comparisons of dental morphology with extant analogs. Here, we use
>> biomechanical and morphometric methods to investigate the dental
>> morphofunctional diversity of early dinosaurs in comparison with
>> extant squamates and crocodylians and predict their diets using
>> machine learning classification models. Early saurischians/theropods
>> are consistently classified as carnivores. Sauropodomorphs underwent a
>> dietary shift from faunivory to herbivory, experimenting with diverse
>> diets during the Triassic and Early Jurassic, and early ornithischians
>> were likely omnivores. Obligate herbivory was a late evolutionary
>> innovation in both clades. Carnivory is the most plausible ancestral
>> diet of dinosaurs, but omnivory is equally likely under certain
>> phylogenetic scenarios. This early dietary diversity was fundamental
>> in the rise of dinosaurs to ecological dominance.
>> https://www.science.org/doi/10.1126/sciadv.abq5201
>
>So basic questions. In modern herbivorous mammals there
>are fore gut fermenters that break down cellulose through
>the use of bacteria prior to the bacteria being attacked by
>hydrochloric acid in a regular stomach or an abomasum. Some
>of them use a rumen and some a pseudorumen.
>
>There are also hind gut fermenters that break down cellulose
>using bacteria in the intestine after passing through the
>acid stomach.
>
>Modern birds have no teeth but there are fossil teeth for
>herbivorous dinosaurs.
>
>Many modern birds have a crop - a modified esophagus for
>storing food, a proventriculus - an acid stomach, and
>then a gizzard - a grinding organ often with gizzard
>stones after the acid stomach.
>
>Were there a lot of dinosaurs that were fore gut fermenters,
>breaking down cellulose in the crop prior to something like
>a proventriculus, or were most hind gut fermenters, generally
>using gizzards for fine grinding with cellulose being broken
>down likely by bacteria in the intestine or cecum?

Hardly anything is known about the intestinal anatomy from fossils of
non-avian dinosaurs, except Scipionyx, a theropod.
See:
https://www.researchgate.net/publication/40662636_Exceptional_soft-tissue_preservation_in_a_theropod_dinosaur_from_Italy

and part II (p.129) on soft tissue anatomy in the monograph on that
taxon:
https://www.researchgate.net/publication/231347243

Gastroliths are known from ornithischians and sauropodomorphs, which
might suggest some form of gastric mill.
See for example:
https://www.app.pan.pl/article/item/app53-351.html