Since standard DNA extraction methods involve at least partial specimen destruction [4], [5] they are unattractive for use on rare or otherwise important specimens (e.g. type specimens, voucher specimens).
In cases in which multiple individuals were available from the same colony, entire or partial specimens were destructively extracted; in cases in which only a single or a few specimens were available, specimens were non-destructively extracted.
After different aging stages, the specimens were subjected to accelerated carbonation experiments, and partial specimens were examined by scanning electron microscopy.
Six main partial specimens of Spinosaurus have been described.
Carapace: (partial specimens available only) Frontal margin of adult straight or slightly convex from anterior aspect; with single anterolateral tooth behind exorbital angle; outer margin of exorbital angle strongly inturned; frontal area with fine, scale-like pattern typical of genus; hepatic and branchial areas with numerous transverse ridges; intestinal area smooth.
They are covered by a partial veil in young specimens.
The type specimen is a partial skull, collected in the summer of 1884 from an outcrop of the Horseshoe Canyon Formation alongside the Red Deer River, in Alberta.
This latter species, known from Ethiopia and, possibly, Kenya at 4.4 million years ago, is the best known of the four and is represented by more than 100 specimens, including a partial skeleton (e.g., White et al. 2009).
The palatal complex of Acrocanthosaurus was known previously from a right palatine and ectopterygoid of SMU 74646 and a partial right ectopterygoid from the holotype specimen.
Ectopterygoid material was previously referred to Acrocanthosaurus, including a partial right ectopterygoid from the holotype specimen [23] and a right ectopterygoid from SMU 74646 [21].
