Sunday, August 17, 2014

Chuanqilong and Tambatitanis

So I finish the Generic History of Dinosaur Paleontology series on July 20th, and four new genera come along. Of course, it's not quantity but quality, and a year with Anzu and Kulindadromeus will be remembered fondly. Every dinosaur should have its day, though, even if they aren't enormous crested caenagnathids or feathered ornithischians. Two of the most recent genera are in freely accessible publications and represent significantly different but still generally overlooked branches of the dinosaurian tree. They are the titanosauriform sauropod Tambatitanis and the ankylosaur Chuanqilong.


The record of dinosaurs from Japan is limited. Not counting Nipponosaurus from Sakhalin Island, now part of Russia, there are five genera known from Japan that are not based on teeth (sorry, Wakinosaurus), all from the Early Cretaceous: possible basal horned dinosaur Albalophosaurus, theropod Fukuiraptor, iguandont Fukuisaurus, titanosauriform Fukuititan, and the subject of this section. (You may think three "Fukui-" are quite enough, but there are still plenty of possible combinations: Fukuicephale, Fukuiceratops, Fukuidon, Fukuidromeus, Fukuignathus, Fukuimimus, Fukuinykus, Fukuipelta, Fukuisaura, Fukuispondylus, Fukuisuchus, Fukuitholus, Fukuityrannus, and Fukuivenator, for example. All it would take is one productive site and a scientist with a strange sense of humor.) There are also ten-odd informal names that accidentally hit the dinosaur dictionaries around 1988–1990, associated mostly with teeth. Tambatitanis may be based on the most material yet. Let's get the basic facts out of the way first:

Genus and species: Tambatitanis amicitiae, the genus name being a reference to the Tamba region and the species name from the Latin for friendship, because the bones were found by two friends (Murakami Shigeru and Adachi Kiyoshi)
Citation: Saegusa, H., and T. Ikeda. 2014. A new titanosauriform sauropod (Dinosauria: Saurischia) from the Lower Cretaceous of Hyogo, Japan. Zootaxa 3848(1):1–66.
Stratigraphy and geography: "Lower Formation" of the Sasayama Group, lower? Albian Stage (Lower Cretaceous), Kamitaki Quarry, Sannan-cho, Tamba City, Hyogo Prefecture, southwestern Honshu, Japan
Holotype (specimen on which a name is based) and known material: MNHAH D-1029280 (Museum of Nature and Human Activities, Hyogo, Japan), a fragmentary partial skeleton including the braincase, part of the lower jaw, partial and whole neck, back, hip, and tail vertebrae, ribs, chevrons (the little bones that hang out, literally, beneath tail vertebrae), and part of a hip

The bones were found with abundant smaller fossils including frog skeletons, lizard teeth and jaws, and teeth of theropods, ankylosaurs, and near-hadrosaurs. The rocks are reddish mudstones interpreted as floodplain deposits. Whole sauropod bones and thousands of bone fragments were present at a single level, and the absence of duplication suggests that the bones all belonged to one individual. Damage on the surfaces of bones that were facing up in the bed indicate that the first burial event didn't entirely bury the bones. The most complete chunk of the skeleton is a section of hip verts and the first ten tail verts, more or less articulated. Tambatitanis can be distinguished from other sauropods by several characteristics, mostly in the vertebrae. You're welcome to click on the link above for the monograph and check them out, but you probably won't get much out of them unless you're a sauropod specialist. The most obvious character to the unaided eye is the shape of the spines on the tail vertebrae, which look like recumbent hooks. They have received their own write-up in SV-POW!, but what exactly they portend is unknown at this point. I suppose there would be some functional difference in muscle attachments. Proportionally, the chevrons are also quite long, which you'd notice in a mounted skeleton and again suggests there was something different going on with the tail compared to other sauropods. It was not a particularly large sauropod. To give you an idea of scale, the tallest tail vertebra that could be measured was 415 mm high (a little less than 16 3/8 inches). A phylogenetic analysis found Tambatitanis to be part of a group of East Asian Early Cretaceous sauropods sometimes called euhelopodids, logically enough after Euhelopus. If it took after Euhelopus, another smallish sauropod, it would have had a proportionally long neck and long arms. The euhelopodids are basal titanosauriforms, effectively meaning they were related to titanosaurs but weren't members of that group. "Basal" is where "primitive" used to be used, but "primitive" has some unhelpful baggage. One caveat for Tambatitanis is that the braincase shows some titanosaur features, so potentially Tambatitanis was a titanosaur or the braincase belonged to something else (always a risk with bonebeds).

From Saegusa and Ikeda (2014); the spines on sauropod tail vertebrae don't usually do that.


Unlike Japan, the Chinese dinosaur record is anything but limited. Chuanqilong is the third genus of ankylosaur from the Cretaceous of Liaoning alone. Ankylosaurs don't get quite the attention that many other groups get. There are a couple of factors behind this. First, although they are not as rare as their reputation may suggest, they aren't common, either. Second, all fossils are like jigsaw puzzles without boxes. Ankylosaur skeletons are like jigsaw puzzles with a few hundred extra pieces that don't connect to the main puzzle but can't be ignored. These extra pieces make up their bony armor, taking on a variety of shapes from small nubbins of bone to large plates and spikes. Note that the cool kids call the armor pieces osteoderms, but we're here, so you don't have to worry about that. The facts for Chuanqilong, as with Tambatitanis:

Genus and species: Chuanqilong chaoyangensis, the genus name a combination of "Chuanqi" as a reference to western Liaoning's fossils and "long" for "dragon, and the species a reference to the region (-"ensis" is the suffix used when you want to refer to a place, like "canadensis" or "mongoliensis" or "sinensis")
Citation: Han F., Zheng W., Hu D., Xu X., and P. M. Barrett. 2014. A new basal ankylosaurid (Dinosauria: Ornithischia) from the Lower Cretaceous Jiufotang Formation of Liaoning Province, China. PLoS ONE 9(8):e104551.
Stratigraphy and geography: Jifuotang Formation, Aptian Stage (Lower Cretaceous), Baishizui Village, Goumenzi County, Lingyuan City, Liaoning Province, China
Holotype and known material: CJPM V001 (Chaoyang Jizantang Paleontological Museum), most of an associated skeleton minus the snout and much of the tail

The Jiufotang Formation is the younger of two formations in Liaoning (the other being the Yixian Formation) that are renowned for their well-preserved Early Cretaceous fossils, especially of various feathery theropods of both the bird and non-bird persuasions. Chuanqilong is the second ankylosaur described from these rocks, the first being Liaoningosaurus from the Yixian. The only known specimen of Chuanqilong is a "roadkill", laid out across a slab. The exposed parts represent the underside of the body, so we can't see what the top of the skull looks like, for example. The animal was about 4.5 m long (14 ft or so) when it died, but was not fully grown. For reference, the femurs, or thigh bones, are 40 cm long (a little less than 16 in), slightly smaller than those of the Gargoyleosaurus pictured in this post. Some armor is visible, but not the stereotypical pavement, probably a reflection of both the underside being the visible side and the relative youth of the individual. As with Tambatitanis, it is distinguished from others of its ilk by various anatomical details. The upper arms were relatively long, and the tooth row of the lower jaw is at about the same height as the articulation point with the upper jaw, which may not seem interesting except in herbivorous dinosaurs the joint is usually lower than the tooth row, apparently because of how force is applied along the tooth row. Like Liaoningosaurus, it sorts out as a basal ankylosaurid, and they may have been related, although some of this may be due to the youth of the only known specimens. Incidentally, although the family Ankylosauridae is historically famous for tail clubs, basal ankylosaurids like Chuanqilong and Liaoningosaurus didn't have them. We all have to start somewhere.

From Han et al. (2014): one slab of ankylosaur coming right up. "Abbreviations: ca, caudal vertebrae; cb, cervical band; da, dermal armor; dr, dorsal rib; lfe, left femur; lfi, left fibula; lhu, left humerus; lil, left ilium; lis, left ischium; lma, left maxilla; lmd, left mandible; lmt, left metatarsal; lra, left radius; lsc, left scapula; lti, left tibia; lul, left ulna; mc, metacarpals; orb, orbital; pl, plates; q, quadrate; rfe, right femur; rfi, right fibula; rhu, right humerus; ril, right ilium; rma, right maxilla; rmd, right mandible; rmt, right metatarsals; rra, right radius; rsc, right scapula; rti, right tibia; rul, right ulna; sar, sacral rib; te, tendons."

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