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.

Extinction and Escalation c 69 Ma

Previous posts mentioned the demise of centrosaurines and survival of chasmosaurines. This post examines the actual transition, around middle Maastrichtian time, and the specific taxa involved. It is interesting that well-armed chasmosaurines--forerunners of Triceratops--appeared concurrently, more or less, with the disappearance of the last centrosaurine. And both coincided with the advent of the archpredator.

Known from a high latitude paleoenvironment (in Alaska) Pachyrhinosaurus perotorum was the last species of its genus, and the last of the centrosaurines. P. perotorum vanished around 69 m.y.a. It's noteworthy that Tyrannosaurus first appeared around this time. Tyrannosaurus replaced Albertosaurus, which apparently disappeared c 69 m.y.a. Clearly, this represented predator escalation; a quantum leap in the threat level facing herbivores. Chasmosaurine escalation was in response to it. Apparently unable to adapt in time, P. perotorum succumbed.

At least four chasmosaurine taxa lived right after P. perotorum. Presumably the four evolved as P. perotorum vanished, and outlasted it. Discovered in the uppermost Horseshoe Canyon, Eotriceratops clearly anticipated Triceratops. So did the roughly coeval SW taxa Ojoceratatops and Torosaurus utahensis. Another close relation, Regaliceratops, differed from the other three in that it resurrected the prominent nasal horn of Styracosaurus. In other words Regaliceratops converged with centrosaurines--not the deescalated later ones but the well-armed taxa preceding them. Although atypical for a chasmosaurine, a prominent nasal horn was a good antipredator weapon. No doubt, Regaliceratops was better able to withstand the archpredator than the virtually hornless P. perotorum. It does not, however, appear widespread or numerous, hence not as successful as the lineage with large orbital horns, culminating in Triceratops.

This intepretation has a potential problem: Apparently known only from the SW or Alamosaurus bearing units at first, Tyrannosaurus may not have impacted mid Maastrichtian taxa in northern areas. At least two of the chasmosaurines, however, Ojoceratops and Torosaurus, existed in the SW. The similarity of Eotriceratops to these genera suggests interaction with the more southerly faunas (which as the North Horn indicates, extended northward, perhaps even farther than Utah). Like Torosaurus, Eotriceratops may have ranged into both northern and southern biomes. Ceratopsians probably migrated regularly in search of food, hence were exposed to the archpredator in some areas even if they weren't affected in all of them, initially. As for P. perotorum, its far northern location didn't ensure safety from Tyrannosaurus. Like other ceratopsians, P. perotorum probably migrated southward. In addition, the archpredator is thought to have entered Laramidia via the Bering area, in which case the Alaskan habitat of P. perotorum may have been the first to be affected.

Eotriceratops. A forerunner of Triceratops, Eotriceratops lived around 68.8 m.y.a.--essentially at the same time, or right after, the last centrosaurine disappeared (c 69 m.y.a.). As was noted in previous posts, the centrosaurines were at a disadavantage because they had evolved a nasal boss, from which it was apparently impossible to re evolve a nasal horn. In contrast chasmosaurines, retaining horns since the Campanian, simply improved upon their defense.

Ojoceratops a taxon of about 68 m.y.a.

Holotype skull of Regaliceratops, showing the prominent nasal horn. It may have lived 68.5 m.y.a. or soon after the faunal turnover spurred by Tyrannosaurus.

Centrosaurine and Lambeosaur Extinction

Compared to lambeosaurs such as Parasaurolophus (right) Edmontosaurus had more economical means of intraspecific interaction, such as mating calls, as it did not rely on extensive, bony structures for this.

Likewise, compared to earlier ceratopsians, pictured above, Triceratops (pictured below) made relatively little investment in means of intraspecific interaction such as sexual advertizing or display (the likely purpose of elongated frills or frill spikes, some bent inward alongside the frill hence useless as weapons). Note the nasal boss of Achelousaurus (above right).

Previous posts attributed the demise of North American centrosaurines and lambeosaurs to the advent of Tyrannosaurus. But what made centrosaurines and lambeosaurs vulnerable while chasmosaurines and edmontosaurs survived? The failure of centrosaurines appears easy to explain. Lambeosaurs were also at a disadvantage even if their specific weakness is not as easy to discern.

In late Campanian time, centrosaurines underwent a process of deescalation. This resulted from the bearpaw transgression. By diminishing habitat and prey populations, the bearpaw seriously affected the most sensitive, upper part of the food pyramid, the predators (tyrannosaurs). Whereas Styracosaurus faced Daspletosaurus wilsoni, the acme of daspletosaur prowess, later centrosaurines knew the less impressive Daspletosaurus horneri and the smaller Albertosaurus. As the tyrannosaur threat waned, the means of battling them became less important. Centrosaurine evolution began to emphasize intraspecific interaction. The deadly nasal horn of Styracosaurus became thhe bent horn of Einiosaurus. The horn disappeared altogether in the later taxa Achelousaurus and Pachyrhinosaurus. Both sported a nasal boss, fine for pushing and shoving matches with others of their kind but of limited use against tyrannosaurs.

Deescalation was permissable in early Maastrichtian time but soon proved fatal. Confronted with a quantum leap in predatory danger, in the form of Tyrannosaurus, centrosaurines could not cope. Retaining horns throughout Campano-Maastrichtian time, chasmosaurines found it easier to adapt. They and their horns just became larger. In contrast, centrosaurines could not easily re--evolve horns from a nasal boss.

It's fallacious to assume centrosaurines were eliminated overnight, or in a few years. They just lost the competition for available niches--niches taken by the better-armed chasmosaurines. Pachyrhinosaurus was not helpless, just at a disadvantage. Regaliceratops and Eotriceratops--forerunners of Triceratops--were more likely to repel a derived tyrannosaur. Even if chasmosaurines were just 10% more likely to survive an attack, it would've meant a (geologically) rapid replacement of centrosaurines.

No doubt, the same applied to hadrosaurs. Given their substantial investment in cranial crests, for sound production (and species recognition) lambeosaurs could not focus on surviving predators to the same degree as Edmontosaurus. It's not so obvious, though, what their specific vulnerability was. Perhaps the crest meant a larger auditory area of the brain at the expense of other means of detecting predators, such as olfaction. But expanded premaxillary and nasal bones (i.e. crests) were unlikely to have diminished a lambeosaur's sense of smell (even if olfaction wasn't the crest's primary function). Perhaps vision was the achilles heel. Lambeosaurs might not have seen an approaching enemy as well as edmontosaurs, even if they could hear and smell a threat just as well.

The lambeosaur disadvantage may not seem significant. Perhaps lambeosaurs were only about 5% more likely to be surprised, and caught, than an edmontosaurine. But again, even a small disadvantage could mean the geologically rapid replacement of one group by another. Few if any lambeosaurs existed in the lastest Maastrichtian of Laramidia, documented by the Hell Creek and equivalents.

It's noteworthy that the last known lambeosaur in North America, Hypacrosaurus, had a smaller crest than Campanian taxa. Lambeosaurus magnicristatus and Parasaurolophus had the biggest crests, but did not last very long. Lambeosaur diversity soon waned in Laramidia. Hypacrosaurus is the only known post Campanian taxon, yet it was not well-suited to survive the archpredator. Compounding the drawback of a crest, Hypacrosaurus had elevated neural spines, probably for display. Not surprisingly, Tyrannosaurus inflicted the coup de grace.

It may not be entirely clear why certain taxa vanished with the advent of the archpredator. But the drawbacks of certain features, coupled with the prowess of T.rex, points to the latter as the probable cause.

The Nemesis of Lambeosaurs

The dinosaurs from the Amur localities (Udurchukan and Yuliangze formations) appear highly unusual, considering their middle Maastrichtian age. They are geologically younger than Nemegt taxa, yet appear older, as if they were a revival of the Campanian. Unlike the Nemegt and the Hell Creek (and equivalents) Amur units yield numerous lambeosaurs, and lack derived tyrannosaurs. In view of this the Maastrichtian age given for the Udurchukan and Yuliangze once seemed dubious, yet it is well established. How can the Amur faunas, so unusual for their place and time, be explained?

They may be explained by delays in the radiation of derived tyrannosaurs, prior to the latest Maastrichtian. The geological record indicates tyrannosaur giants were initially confined to certain areas. Their impact was profound but it was long limited geographically. Around middle Maastrichtian time certain regions, including the Amur, were unaffected. This meant a remarkable disconnect between the big tyrannosaur environments and the others. A comparison of the Zhucheng and Laiyang localities of the Wangshi series, and the Javelina and Horseshoe Canyon formations, reveals striking faunal differences, even among close coeval units, reflecting the presence or absence of advanced tyrannosaurs.

The archpredators appear to have evolved in continental interior habitats with titanosaurs or the giant Shantungosaurus. Initially, they eschewed the wetter environments preferred by most hadrosaurs. Eventually, however, the super hunters spread, to the detriment of taxa which, long unexposed to them, lacked coevolutionary preparation to cope. Lambeosaurs and primitive hadrosaurs faced annihilation.

Essentially, the crested taxa could not survive alongside the later, giant tyrannosaurs. No lambeosaurs existed in the Nemegt paleoenvironment where Tarbosaurus was top predator. Likewise Tyrannosaurus habitats appear devoid of lambeosaurs. The latter are, however, known from the early-mid Maastrichtian Horseshoe Canyon, where the top predator was the less derived Albertosaurus. It is noteworthy that Tyrannosaurus was evolving by this time (c 69 m.y.a.) but only in the Alamosaurus habitats. Wangshi localities provide another example. The habitat of Zhuchengtyrannus, like that of Tyrannosaurus, included an edmontosaurine, Shantungosaurus, but no lambeosaurs. In sharp contrast the Laiyang exposures, where no big tyrannosaurs are known, have yielded the lambeosaur Tsintaosaurus and the primitive Tanius. Apparently, presence or lack of derived predators explains the vast difference in faunas despite the proximity of the two coeval habitats (Laiyang has the anklosaur Pinacosaurus also known from Mongolian strata dated c 73 ma, about the same age as Zhucheng strata--which also have the similar Sinankylosaurus).

A big tyrannosaur from the late Maastrichtian Dalangshan formation of southern China and a possible edmontosaur, Microhadrosaurus, suggest the same pattern.

Where huge tyrannosaurs were not yet present, lambeosaurs still held out. The Amur region, therefore, can be compared to the coeval, upper Horseshoe Canyon. In both paleoenvironements, lambeosaurs were at least temporarily safe.

Like Hypacrosaurus, Olorotitan, Amurosaurus and other crested forms thrived in the absence of Tyrannosaurus or a comparable taxon. Some lasted into early late Maastrichtian time, the age of the Blagoveschensk beds yielding Amurosaurus. It's possible, though, they succumbed in the last million years or so of the Maastrichtian. By then, the spreading Tyrannosaurus extirpated Hypacrosaurus, the last of the North American lambeosaurs, and other taxa. As the Dalangshang teeth indicate, large tyrannosaurs still existed in Asia toward the end. Like their North American counterparts, they may have extended their ranges into lambeosaur refugia, dooming the crested taxa.

Teeth of a large tyrannosaur from the late Maastrichtian of southern China.

Eclipse 2024

Yesterday in CT the eclipse, although partial, covered over 90% of the sun, causing darkening after 3 p.m. The above pic was taken soon after the eclipse began. It isn't great, but clearly shows the situation after 2 p.m. I was impressed by how rapidly the event progressed.

The Last Stegosaur

Yanbeilong ultimus is too poorly known to be restored. The above restoration is based on late Jurassic taxa and is probably inaccurate

The latest stegosaur to be named, Yanbeilong ultimus, is important for what it tells us about the stratigraphy and extinction of plated dinosaurs.

Like stegosaurs from the Louhandong and Kukhtekian beds,Yanbeilong is based on just pelvic and vertebral elements. Discovered in the Zuoyun formation of Shanxi province, China, it consists of a sacrum, both ilia, the left ischium, the right pubis, seven dorsal verebrae and one caudal. The holotype lacks cranial or limb bones. Unlike the Hebei material, Yanbeilong is of limited value to taxonomists.

The new taxon can, however, shed much light on the demise of Stegosauria--both the timing and cause of that event. With the possible exception of Dravidosaurus, Yanbeilong is the geologically youngest stegosaur known. Unlike Mongolostegus, Wuerhosaurus and the Louhandong specimen, which are not precisely dated ("Aptian-Albian" or in the case of Wuerhosaurus "Valanginian-Albian") Yanbeilong is unambiguously dated. The Zuoyun is of Albian age. This places Yanbeilong at the end of the early Cretaceous. No other stegosaur definitely occurs as late as the last stage of the EK.

An Albian age is interesting inasmuch as no stegosaur is known from the subsequent Cenomanian stage. The Baynshiree formation, for example, never yielded a stegosaur and nor did Iren Dabasu. It seems reasonable to infer that Stegosauria essentially went out with the EK or Albian. Realizing Yanbeilong was the denouement of Stegosauria, Chinese researchers gave it the species name "ultimus"--the last.

Why did stegosaurs vanish in the Albian, or by the end of that stage? Studies have noted evidence for drastic climatic change in Asia, accompanided by floral change, around the end of that period.

Krassilov et al. note the appearance of Sequoia in Mongolia "indicates a radical change from subtropical redbed climate of pronounced seasonal dryness towards more humid and equable conditions. A climate change like this must have inflicted a major restructuring of terrestrial ecosystems at about the Albian-Cenomanian boundary."

Golozoubov et al. report similar findings. In the Partizansky basin of far eastern Russia, "The late Albian saw a sharp change of vegetation...Diversity markedly decreased...numerous warmth-requiring species became extinct...the released niches occupied by angiosperms." In the Razdolnensky basin "..diversity sharply decreased in the Albian...Many of the cycadophytes, conifers and ferns became extinct."

Loss of cycadophytes and bennetitales, in particular, likely proved fatal to stegosaurs. Their niches taken by angiosperms, the cycadophytes never revived, and nor did the stegosaurs requiring them. Drastic climate change, specifically wetter habitats, spurred the change.

Climate/floral transition, the root of the stegosaur demise, did not occur everywhere at once. There is evidence for it at the start of the EK as well as its end. In western North Ameria, the Jurassic-Cretaceous boundary saw a wetter climate. Stegosaurs, notably the iconic Stegosaurus, thrived in the late Jurassic of America, in dry, upper Morrison habitats. But they are unknown after the wetter Jurassic-Cretaceous transition. None have been found in the lower Yellow Cat sediments. Since increased rainfall proved inimical to American stegosaurs, it isn't surprising that the same conditions were their nemesis in Asia. Dry habitats apparently persisted longest in Asia, but the late Albian finally witnessed the fatal change. Wetter conditions, resulting from a severe highstand, extirpated the last stegosaur.

References

Krassilov et al. New Fossil Plant and Insect Records Bearing on Cretaceous Climate of Western Gobi, Mongolia. American Journal of Plant Biology Vol. 2, No. 2, 2017 pp 43-48.

V. Golozoubov et al. Early Cretaceous change of Vegetation and Environment in East Asia Paleogeography, Paleoclimatolgy, Paleoecology 153, 1999 pp 139-146

Addendum

Dorsal vertebrae of Yanbeilong ultimus

The vertebrae have higher neural arches than those of other stegosaurs, and their neural canals are smaller. Yanbeilong is also distinguished by incomplete fusion of the sacrals (possible evidence for immaturity?). I'm not sure of the functional significance of small neural canals. High neural arches probably evolved to maximize the height of the stegosaur's back, making it appear more formidable (like the plates; a cat arches its back for the same resason). Not surprisingly, Yanbeilong is considered most closely related to Wuerhosaurus and Stegosaurus but differs from them.

Old Teachers

Above, a pic of second grade teacher Mrs. Lucy Sweeney (formerly Miss Shea) the most recently deceased of the teachers I had.

Not surprisingly, as a person grows older, he outlives many of the adults he once knew, including teachers. Below, I summarize the fates of those I've had.

Bentley elementary school Manchester CT (torn down in 2008):

Kindergarten teacher: Mrs. Kirby died around 1995.

First grade teacher (1964-65): Miss Lillian Curtis whereabouts and fate unknown.

Second grade teacher(1965-66): Miss Lucy Shea, died January 6, 2024.

Third grade teacher: Miss Freeman, still alive.

Fourth grade teacher Mrs Lillian Simmers died September 2007. Another 4rth grade teacher, Miriam Thayer, passed away at the end of 1998.

Fifth grade teacher Mr. Gessay still alive at this writing.

Sixth grade teacher Mrs Saunders passed in December 1994. Another teacher I had in 6th grade, Mr. Ewald, died in 1992.

Illing Junior High (1970-72):

Homeroom teacher Mr. Cox deceased for several years.

Science teacher Mr. von Deck died in 1981

Gym teacher Mr. Kelly died in 2020.

Mrs. Norling social studies teacher died in 2010.

Mrs. Segar english teacher passed in 1996.

Mr. Hadigian math teacher died in 2015.

Mrs Parks music teacher died in 2006.

East Catholic High School 1972-73:

Mrs. Farrell math teacher died 1992

Mr. Adamchak science teacher died 2022.

Mr. Richard history teacher passed in 2018.

Manchester High School 1973-76:

Mr. Glaeser history teacher died 2001.

Mr. Perry science teacher died 2002.

Mrs. Yuska english teacher died 2005.

Mr. Burnet math teacher died 2005.

Mr. Sines science teacher died 2006.

Mr. Zatursky history teacher died 2007.

Mr. Stearns english teacher died 2007.

Mr. Vincenzo science teacher died 2008.

Mr. Hyde math teacher died 2010.

Mrs. Don english teacher died 2016.

In the "ancientfaces" site I wrote voluminously on some of these people notably Mr. Glaeser, Mrs. Don and Mrs. Yuska.

Lucy Sweeney (nee Shea) with husband Joe and others at a reunion.