Dating Error

Desmond's The Hot Blooded Dinosaurs is an old, mid 70s book. It's main purpose is to show that dinosaurs were endothermic not gargantuan reptiles. The book also addresses the issue of extinction. At the time, the impact theory was not established and other views were still in vogue. The author noted evidence for a gradual demise instead of a sudden, catastrophic one. Among both dinosaurs and ammonoids, diversity in North American waned before the end. Desmond mentioned other evidence: eggshell pathologies in Europe. Unknown at the time, these do point to extinction but it was only partial, and not associated with the K-Pg. A summary of the book's view:

Can we ever witness the suffering of dinosaurs towards the end? What evidence could reveal the anguish of creatures separated from us by 70 million years? The last dinosaurs were subjected to unbearable pressure. That much is certain. Evidence comes from the French Pyrenees. As Professor Erben noted, local eggs display features indicative of a crisis. The strata in which the eggs are found are of late Maastrichtian age and therefore cover the period of time immediately prior to the final extinction of the dinosaurs. Erben's analysis has had startling and unforeseen results. The stratigraphically highest eggs display thinning; shell thickness fell from 2.5mm to just 1mm. In birds, thinning of eggshell is associated with stress from predation, poisoning etc. In the latest Cretacous, this condition proved fatal as a fetus could not derive enough calcium to build a skeleton. Desmond's conclusion: "The majestic dinosaurs....had departed not with a bang but with a whimper--the whimper of the young as they perished incarcerated in tiny prisons."

The problem is, the dating of the Pyrenees strata was erroneous. The strata are of middle Maastrichtian age, and therefore irrelevant to the final extinction. Although stress, reproductive issues and extinction really happened, only local taxa were affected and they were replaced. The crisis resulted from an influx of lambeosaurs into western Europe. Blasisaurus and others outcompeted local titanosaurs, rhabdodonts and ankylosaurs. Loss of their niche severely stressed the titanosaurs. The result was pathology and extinction. But dinosaurs generally lived on, until the K-Pg three million years later.

Assigning a late Maastrichtian age to a somewhat older unit was once common. Because of widespread erosion at the K-Pg, the geological record is strongly biased against late Maastrichtian strata. The North American record is an exception. Elsewhere, units of 71-68 Ma are the youngest Cretaceous horizon hence were often mistaken for the end. Examples include the Sanpetru formation of Romania and the Amur localities of east Asia. Evidence from such units has no bearing on the final demise.

Eggshell pathologies do occur in close proximity to the K-Pg elsewhere, in southern China. Researchers have documented eggshell anomalies in the Nanxiong. However, even these predate the K-Pg and the presumed cause was different. In India, Deccan volcanism spewed chemical pollutants into the atmosphere. Transported to southern China by the wind, the pollutants adversely affected the local biota. Nanxiong pathologies suggest extinction, albeit of limited geographical extent. Contaminated eggshells may be the only evidence for a Deccan role in the K-Pg. Chicxulub was undoubtedly the main cause. (Tyrannosaurus seems to have had an impact c mid Maastrichtian but a subsequent role, while possible, is quite speculative.)

References

Desmond, Adrian. The Hot Blooded Dinosaurs Dial Press 1976.

Sellas, Albert. Vila, Bernat. Galobart, Angel. Evidence of Reproductive Stress in Titanosaurian Sauropods Triggered by an increase in Ecological Competition. Scientific Reports 2017.

Below, Desmond's book, published in 1976.