July 26 , 2016

by Justin Tweet

One of the notable quirks of nodosaurids is a predilection for washing out to sea. Nodosaurus textilis and Stegopelta landerensis are a couple of featured examples. We turn now to another species from the Western Interior Seaway: Hierosaurus sternbergii.

While working in the Niobrara of western Kansas in the first decade of the 20th century, Charles H. and George Sternberg of the famous Sternberg fossil collecting dynasty each encountered pieces of bony armor, which they interpreted as shell pieces from undescribed turtles. They notified George Wieland of Yale University (Sternberg 1909). Wieland today is much better known for his paleobotanical work, and also as the central figure of the fiasco known as Fossil Cycad National Monument. At the time, though, he had recently been working on fossil turtles, and was able to identify the remains as coming from heretofore-unknown armored dinosaurs. The Sternbergs then collected additional material. At least two armored dinosaurs are represented in the ankylosaurian remains, based on the presence of two distinct types of cervical half rings, although who exactly collected what from where is not entirely clear, as noted by Carpenter et al. (1995). Charles Sternberg's account describes recovering a pair of scutes from a fragmentary skeleton in 1905, and George recovering six scutes "later" (no year stated, although the natural reading is the same year), with additional skeletal elements collected after Wieland identified the scutes as dinosaurian. With only one skeleton noted explicitly in the text, the first interpretation is that the bones collected later were from the original fragmentary specimen observed by Charles, not George's specimen, which for all we can tell from the account was just six scutes. Wieland (1909) reported getting two paired elements in 1905 and then a shipment of six elements in 1908, the latter of which he named Hierosaurus sternbergii in Charles H. Sternberg's honor (Wieland was under the impression that Charles collected them; today this would probably be sternbergorum, honoring all of them collectively). In 1911 he reported getting additional fragmentary material belonging to the type, which Sternberg had not collected at first. There are two ways to make Sternberg's and Wieland's accounts consistent: we assume that the skeleton collected by the Sternbergs was not Charles's specimen, but George's specimen, and Charles did not firmly distinguish which one he was writing about; or, we assume that the skeleton was indeed Charles's, and Wieland was confused or misinformed about what he was receiving. For what it's worth, today there are two catalog entries in the Yale collections for the fossils, one (YPM 1847; link includes a photo of three osteoderms) which is the holotype of Hierosaurus sternbergii and includes skull fragments, rib fragments, at least 34 scutes, and at one time vertebrae and phalanges; and the other, YPM 55419, consisting of the original two scutes (Carpenter et al. 1995). The moral of the story is to document your finds in detail and write with clarity.

Enough of that. Wieland's (1909) original description does about as much as could be done in 1909 with a handful of scutes. With cervical half rings not yet known to be a standard piece of ankylosaurian anatomy, he interprets the fused scutes shown above as belonging to the neck or the tail. He does note that the fused pair illustrated as 7/7a may not belong to Hierosaurus sternbergii, which seems like a good conclusion to me. Aside from one nubbin, the type scutes are rather oval in shape, and all feature prominent keels, sometimes pointed at one end. Sternberg (1909) described them as "diamond-shaped with rounded angles" with filler scutes between them. Wieland (1909) compares his new species most closely to Polacanthus, and then goes on a tangent comparing the evolution of armored dinosaurs to turtles, going back to his experience with the latter group.

A couple of years later (1911) Wieland was able to contribute more details, based on the recovery of additional scutes, plates, and fragments which he attributes to the type specimen. A couple of pointed plates are impressively sized, and the figured example looks quite Sauropelta-like, as noted by Carpenter et al. (1995). One spike is interpreted as bearing two points, although it's not clear from the restoration what this interpretation is based on. The most unusual addition is two pieces of curved bone with nodes sticking out from the curve. Wieland interprets this as part of a squamosal, giving the animal a Triceratops-like frill (unfortunately, there is no life restoration). Carpenter et al. (1995) consider this to more likely represent part of the parietal. Wieland reports that there are nearly 70 "keels" (his term for the large scutes in this paper, which is fitting enough because all of the pieces illustrated are indeed strongly keeled), which means that half of them went missing before Carpenter et al (1995) saw the material. Because he has not been able to find a sacral shield, he regards the armor as representing only the body in front of the hips, which is a reasonable enough proposition. He estimates the animal as about 4 m (about 13) long, and distinct from the larger Stegopelta per Williston (for one thing, its armor is not scrobiculate!). (As we saw in the Stegopelta post, Moodie [1910] thought they might be synonyms.) In hindsight, the strongly keeled scutes are reminiscent of Edmontonia and Panoplosaurus; Ford (2000) suggests a relationship with Panoplosaurus, drawing attention to the oval bases, but the pointed keels look more Edmontonia rugosidens to me. Maybe a happy medium? The addition of Sauropelta-like cervical spines would have made a distinctive-looking beast, provided, of course, that the armor is all part of the holotype (the omnipresent oval shapes and keeling suggest that the animal that provided Charles Sternberg's half-ring is not involved).

Hierosaurus has not garnered much attention since Wieland's time, although it did become a recipient of a second species, H. coleii (Mehl 1936). You may know this one as Niobrarasaurus, described as its own genus in Carpenter et al. (1995). Like Stegopelta, the genus Hierosaurus spent the 1980s as a synonym of Nodosaurus following Coombs (1978). Carpenter et al. (1995) dissolved the synonymy, but found H. sternbergii to be indeterminate.

References:

Carpenter, K., D. Dilkes, and D. B. Weishampel. 1995. The dinosaurs of the Niobrara Chalk Formation (Upper Cretaceous, Kansas). Journal of Vertebrate Paleontology 15(2):275–297.

Coombs, W. P. 1978. The families of the ornithischian dinosaur order Ankylosauria. Palaeontology 21(1):143–170.

Ford, T. L. 2000. A review of ankylosaur osteoderms from New Mexico and a preliminary review of ankylosaur armor. Pages 157–176 in S. G. Lucas, and A. B. Heckert, editors. Dinosaurs of New Mexico. New Mexico Museum of Natural History and Science, Albuquerque, New Mexico. Bulletin 17.

Mehl, M. 1936. Hierosaurus coleii: a new aquatic dinosaur from the Niobrara Cretaceous of Kansas. Journal of the Scientific Laboratory, Denison University 31:1–20.

Moodie, R. L. 1910. An armored dinosaur from the Cretaceous of Wyoming. Kansas University Science Bulletin 5:257–273. (text) (plates)

Sternberg, C. H. 1909. An armored dinosaur from the Kansas Chalk. Transactions of the Kansas Academy of Science 22:257–258.

Wieland, G. 1909. A new armored saurian from the Niobrara. American Journal of Science 27:250–252.

Wieland, G. R. 1911. Notes on the armored Dinosauria. American Journal of Science, Series 4, 31:112–124.