Origin of dinosaurs: close to the equator?

Heath et al 2025 suggest
“a low paleolatitude origin for dinosaurs.”

that means near the paleo equator.

That should be easy to figure out.
In the large reptile tree (LRT, 2335 taxa, subset Fig 1) find the last common ancestor of all dinosaurs. That’s easy.

LCA of dinos = Gnathovorax, Herrerasaurus, Staurikosaurus.

Where do we find those? Southern Brazil

What latitude was that 230 mya? 40º below the equator.

Figure 1. Archosauriformes in the LRT. Origin of Dinosauria in red box. Arrows point to Lagerpeton and Silesaurus, too often associated with the origin of dinosaurs and pterosaurs. ” data-image-caption=”

Figure 1. Archosauriformes in the LRT. Origin of Dinosauria in red box. Arrows point to Lagerpeton and Silesaurus, too often associated with the origin of dinosaurs and pterosaurs.

” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/01/archosauriformes588.jpg?w=99″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/01/archosauriformes588.jpg?w=338″ class=”size-full wp-image-91339″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/01/archosauriformes588.jpg” alt=”Figure 1. Archosauriformes in the LRT. Origin of Dinosauria in red box. Arrows point to Lagerpeton and Silesaurus, too often associated with the origin of dinosaurs and pterosaurs. ” width=”584″ height=”1767″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/01/archosauriformes588.jpg?w=584&h=1767 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/01/archosauriformes588.jpg?w=50&h=150 50w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/01/archosauriformes588.jpg?w=99&h=300 99w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/01/archosauriformes588.jpg 596w” sizes=”(max-width: 584px) 100vw, 584px” />

Figure 1. Archosauriformes in the LRT. Origin of Dinosauria in red box. Arrows point to Lagerpeton and Silesaurus, too often associated with the origin of dinosaurs and pterosaurs.

Final step:
Where do proximal outgroup taxa come from?

Lewisuchus – Middle Triassic Western Argentina, 40º below the equator

Saltoposuchus – Late Triassic, Germany, 35º above the equator

Trialestes – Late Triassic, northwestern Argentina, 40º below the equator

Turfanosuchus – Middle Triassic China, 40º above the equator

Essentially these taxa span the Northern temperate to Southern temperate latitudes. None are near the equator.

Turfanosuchus, Trialestes, and Saltoposuchus
were not mentioned in the Heath et al text. Lewisuchus is mistakenly considered a silesaurid. Here (Fig 1) you can see why due to its proximity.

Heath et al wrote,
“Dinosaurs dominated Mesozoic terrestrial ecosystems for 160 million years, but their biogeographic origin remains poorly understood.”

We have the above data. Fossil sites of any age are always mere pinpricks on the globe. What happened between these pinpricks can only be extrapolated.

“the high taxonomic and morphological diversity of these earliest assemblages suggests
a more ancient evolutionary history that is currently unsampled.”

A cladogram that minimizes taxon exclusion (Fig 1) reduces uncertainty.

“Phylogenetic uncertainty at the base of Dinosauria, combined with the subsequent appearance of dinosaurs throughout Laurasia in their early evolutionary history, further complicates this picture.”

And there’s your answer: Currently vague. Represented by pinpricks.

“These results are best supported when silesaurids are constrained as early-diverging ornithischians, which is likely because this topology accounts for the otherwise
substantial ornithischian ghost lineage, explaining the group’s absence from the fossil record prior to the Early Jurassic.”

Don’t make this mistake. Silesaurids are poposaurs (Fig 1).

“Crucially, if silesaurids are not ornithischians, then the earliest ornithischians, and consequently a large portion of the earliest dinosaurs, are essentially absent from the fossil record.”

Don’t make this mistake. These authors are not aware of the Phytodinosauria clade (Fig 3). Many of the earliest phytodinosaurs are also from Southern Brazil, but Daemonosaurus (Fig 2) is from New Mexico, 5º above the Late Triassic equator.

Unfortunately, Daemonosaurus is not mentioned in the Heath et al text.

Figure 1. Daemonosaurus cervicals traced from in situ fossils and compared to sister taxa, Eoraptor, Leyesaurus, Heterodontosaurus and Pisanosaurus. Among these taxa, Daemonosaurus has the largest skull and most gracile cervicals. ” data-image-caption=”

Figure 1. Daemonosaurus cervicals traced from in situ fossils and compared to sister taxa, Eoraptor, Leyesaurus, Heterodontosaurus and Pisanosaurus. Among these taxa, Daemonosaurus has the largest skull and most gracile cervicals.

” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2015/03/daemonosaurus-cervicals588.jpg?w=197″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2015/03/daemonosaurus-cervicals588.jpg?w=584″ class=”size-full wp-image-17720″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2015/03/daemonosaurus-cervicals588.jpg” alt=”Figure 1. Daemonosaurus cervicals traced from in situ fossils and compared to sister taxa, Eoraptor, Leyesaurus, Heterodontosaurus and Pisanosaurus. Among these taxa, Daemonosaurus has the largest skull and most gracile cervicals.” width=”584″ height=”891″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2015/03/daemonosaurus-cervicals588.jpg?w=584&h=891 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2015/03/daemonosaurus-cervicals588.jpg?w=98&h=150 98w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2015/03/daemonosaurus-cervicals588.jpg?w=197&h=300 197w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2015/03/daemonosaurus-cervicals588.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />

Figure 2. Daemonosaurus cervicals traced from in situ fossils and compared to sister taxa, Eoraptor, Leyesaurus, Heterodontosaurus and Pisanosaurus. Among these taxa, Daemonosaurus has the largest skull and most gracile cervicals.

The authors also make the academically acceptable mistake
of linking pterosaurs with lagerpetids. Neither are related to dinosaurs in the LRT.

The authors reminded readers
“Fissure fill deposits in the UK include the early-diverging sauropodomorph
Thecodontosaurus, have traditionally been considered Rhaetian in age but might actually date back to the middle Carnian.”

In the LRT (Fig 3) Thecodontosaurus is a phytodinosaur and not a basal one.
The UK was 30º North of the Equator then.

The authors concluded,
“In summary, our findings show that dinosaurs—and, potentially, archosaurs as a wider group—likely radiated in the low-latitude region of Gondwana, a result that has not been recovered in previous paleobiogeographic estimations.”

Given what we know (see above) this hypothesis of dinosaur origins has not been recovered in previous studies perhaps because it is not precise enough.

References
Heath JA, Cooper N, Upchurch P and Mannion PD 2025. Accounting for sampling heterogeneity suggests a low paleolatitude origin for dinosaurs. Current Biology, CelPress https://doi.org/10.1016/j.cub.2024.12.053

Map of Earth 230 mya, Norian Age of Triassic Period.

Publicity
dailygalaxy.com/2025/01/scientists-just-revealed-where-dinosaurs-really-came-from-this-changes-everything/