[D] Tugulusaurus faciles [dG] [T]
Dong , 1973
Cretaceous Late Valanginian Hauterivian Barremian Aptian
Saurischia Theropoda Tetanurae Coelurosauria Nomina Dubia
Tugulu Group of the Junggar Basin, Lianmugin Formation, Urhe area, Xinjiang Uygur Autonmous Region, northwestern China
Genus - Typespecies
Hindlimb, rib, vertebral centrum.
Rauhut & Xu, 2005: Although based on an incomplete and rather poorly preserved specimen, Tugulusaurus can be shown to be valid on the basis of strongly broadened caudal vertebrae with an anteriorly placed neural arch and a short and highly asymmetrical metacarpal I.
Commments by Mickey Mortimer
\\\"Tugulu lizard\\\", Tugulu being the stratigraphic group it was found in.
(IVPP V 4025) dorsal rib, four mid caudal vertebrae, metacarpal I, manual phalanx I-1, manual ungual I, manual phalanx III-?, femora (one proximal) (210 mm), tibia (230 mm), astragalus, calcaneum, distal metatarsal III, pedal ungual, other fragments.
The coelurosaurian femur and tibia can be distinguished from other coelurosaurs based on gross morphology, although the poor description and figure quality preclude identification of distinct apomorphies. The manual elements can be distinguished from Allosaurus (which they are morphologically closest to) by features noted in the description, but may not be properly referred to Tugulusaurus and cannot be compared to other carnosaurs. If the elements belong to one taxon, the combination of carnosaur and coelurosaur traits would be apomorphic.
The description of Tugulusaurus is translated rather poorly and the plates are difficult to make out details in.
There is a dorsal rib figured. Dorsal ribs aren\\\'t well described or figured in the literature, but some comparisons can be made. It is from the middle of the dorsal column based on the length and curvature. The capitulum is broken, making it look shorter and deeper than in other theropods.
The caudal centra are amphicoelous and longer than wide. The absence of an \\\"edged process\\\" ventrally may mean there was no ventral keel. The ventral edge is concave laterally and the neural spines had \\\"disappeared\\\". Whether the latter statement implies they were originally absent or have broken off, I don\\\'t know. There are bases of transverse processes preserved.
A bone is figured in plate III (5, 6) that appears to be a first metacarpal. This element is very different from coelurosaur first metacarpals, but resembles Allosaurus quite closely. It is much more robust than coelurosaurs and has well-defined distal condyles. The bones only differences from Allosaurus are: narrower lateral condyle, condyles less extensive dorsally and proximolateral process facing more laterally than proximally.
Plate III figure 3 is a manual phalanx I-1. It is also very similar to Allosaurus, being slightly more slender with a deeper proximoventral process. It resembles Alxasaurus slightly as well. The proximoventral process extends proximally past the proximodorsal process, the shaft is straight and the distal expansion extends further proximally ventrally.
Also among the figures (and in the text) is a manual ungual. This ungual is well curved, has a moderate flexor tubercle, a strongly proximally projecting proximodorsal process and no proximodorsal lip. It resembles Allosaurus and Torvosaurus more than any coelurosaur. Among coelurosaurs, it resembles troodontids and the Iren Debasu therizinosaur the most.
Another manual phalanx is figured. It is from the third digit based on robustness and size. Comparison to other taxa is difficult as the exact identity of the phalanx is unknown. It does resemble Allosaurus in general proportions however.
The femur is very slender and hollow with a ridge-like fourth trochantor. The femoral head is declined and the medial condyle projects further distally than the lateral condyle. It is described as being bowed \\\"to the back\\\". It is distinctly sigmoidal in anterior view. Besides these features, the femur is described as having a \\\"crista present on the small twist\\\" (perhaps a crested lesser trochantor?) and \\\"muscle adherant surface rough\\\".
The tibia is 110% of femoral length. It is referred to as a radius in the translation, which explains the rather odd statement that the radius exceeds femoral length in Glut\\\'s encyclopedia. The cnemial crest is \\\"poorly developed\\\" and the medial condyle is more distally projected than the lateral condyle. The shaft expands distally in anterior/posterior view and no fibular crest or astragalar fossa can be observed. Other dubious tibial features include \\\"proximal end ... expands triangularly at front and back\\\" and \\\"distal end ... inserting into calcaneum (astragalus?) fovea like a sharply-cut triangle\\\".
The astragalus and calcaneum are not illustrated, but are stated to be tightly united and the calcaneum is crescentric. There are said to be \\\"twisted processes on both sides of astragalus\\\" and \\\"no conspicuous tibial jacent process (ascending process?).\\\"
The text describes two probable distal ends of metatarsal III that are figured in plate III. I can\\\'t recognize them off hand. Perhaps figures III-8 or 4. They are said to have shiny and smooth articular surfaces and be concave on both sides. An important detail is that Dong states Tugulusaurus differs from other ornithomimids in that the proximal third metatarsal does not constrict. Thus, the arctometatarsalian condition was probably absent.
A pedal ungual is figured (III-1). It is very slightly curved, with a concave ventral margin, shallow dorsoventrally, has a very small flexor tubercle and the proximodorsal corner is placed far proximally to the proximoventral corner. It is most similar to Neovenator, Sinraptor and Nedcolbertia. Compsognathus seems to have similar pedal unguals as well.
Other bones are figured. Some (II-6, 7, 8, III-7, 9, 12, 13) may be the caudal vertebrae described in the text. III-14 is rather indeterminable. Oddly, II-9 resembles the first metacarpal of Archaeornithomimus quite closely. However, II-7, 8 and 9, and III-9 and 14 are labeled as Theropoda, not Tugulusaurus as the other figures are. Perhaps more than one taxon is present.
Dong refers this genus to the Coelurosauria based on hollow long bones and tibia longer than femur, and to the Ornithomimidae based on the outline and characteristics of the tarsometatarsus and phalanges. Molnar thought the tibiofemoral ratio was too small for an ornithomimid. Besides this, the affinities of Tugulusaurus have been ignored. It is generally placed as Coelurosauria incertae sedis.
First, let\\\'s compare it to ornithomimosaurs. The caudal vertebrae are plesiomorphic and could be ornithomimosaurian from the description. The first metacarpal is extremely different from ornithomimosaurs. It is much shorter (even than Harpymimus) with a more medially divergent distal articulation. Compare the first metacarpals of Allosaurus and any ornithomimosaur to see what I mean. Manual phalanx I-1 is not dorsally bowed, unlike advanced ornithomimids and the proximoventral process extends much further proximally than the proximodorsal process does.
The first manual ungual has a proximodorsal process that extends proximally much more than the proximoventral process, unlike ornithomimosaurs. It is also much more curved and deeper than all ornithomimosaurs except Deinocheirus. The phalanx from manual digit III is too short to be III-3 in ornithomimosaurs and too long to be III-1 or III-2, except in Harpymimus. The femur plesiomorphically has a fourth trochantor, like ornithomimosaurs. The possible lack of an arctometatarsus would be more basal than ornithomimosaurs except probably Harpymimus and \\\"Ginnareemimus\\\". The pedal ungual is more curved than ornithomimosaurs, with a more proximally projecting proximodorsal process. Thus, the only similarities to ornithomimosaurs (amphicoelous caudal vertebrae, fourth trochantor present, etc.) are symplesiomorphies.
As was obvious from my description, I felt the manual elements compared very well to Allosaurus. Also, the pedal ungual compares most closely to Neovenator and Sinraptor also carnosaurs. Another character that may support a non-coelurosaur affinity is the inconspicuous \\\"tibial jacent\\\" process, possibly indicating a low ascending process on the astragalus. The only features arguing against this are the high tibiofemoral ratio and the declined femoral head (along with the small size and gracility). Although most of these features could simply be juvenile traits, the declined femoral head is hard to ignore.
It is also quite possible that there are actually two taxa present, a carnosaur and an ornithomimid. This is supported by the lack of forelimb elements in the holotype listing and by a cryptic statement by Dong. \\\"It is likely this claw and this digit belong to the forelimb. At the present, because the phalanx is too large to be regarded to be a forelimb, it is difficult to judge\\\". There are no scale bars or measurement guides for the forelimb material, so this is impossible for me to judge. The forelimbs would be expected to be larger if they were carnosaurian however, so that would make sense if there are two animals present.
Another reason more than one theropod may be represented in the Tugulusaurus material is the fact that two figures (II-9 and III-5, 6) seem to be first metacarpals of different morphologies. II-9 look almost identical to Archaeornithomimus while III-5 and 6 are almost identical to Allosaurus. Finally, carnosaur-like theropods are also present in the Tugulu group, as is shown by the jaw remains of Kelmayisaurus and a distal pubis labeled as \\\"Megalosauridae indet.\\\" (fig. VII-4) that appears carnosaurian, perhaps allosaurid.
If the elements belong to one species, Tugulusaurus is either a very gracile or juvenile carnosaur with an apomorphically declined femoral head, or a derived coelurosaur with a carnosaur-like manus. I find it more likely that two taxa are represented. The femur is coelurosaurian and the tibia probably belongs to the same animal, as might the metatarsal fragments. The manual elements are carnosaurian. The pedal ungual resembles members of both groups and the rib and caudal vertebrae could be from either taxon.
The name Tugulusaurus should apply to whatever genus the hindlimbs belong to, as they are listed in the holotype, unlike the forelimb material. This theropod is probably coelurosaur, due to the declined femoral head, but otherwise hard to place phylogenetically. Declined femoral heads are known in some ornithomimosaurs (eg Archaeornithomimus) and eumaniraptorans. The fourth trochantor would indicate that it is not troodontid, [avian] Avialae or an advanced dromaeosaurid. The caudal vertebrae eliminate alvarezsaurids and pygostylians if they belong to the same animal. If the metatarsals go with the femora and tibia, which is probable, arctometatarsalian taxa are also eliminated. This leaves basal ornithomimosaurs, Protarchaeopteryx and basal dromaeosaurids as possible candidates. The listed holotype material is too poorly described/figured to assign Tugulusaurus to either of these taxa. If the first metacarpal in II-9 does belong to this taxon however, it would be almost certainly ornithomimosaurian .
As for the forelimb material, it resembles Allosaurus more than megalosaurids, based on the less robust first metacarpal and much longer phalanx I-1. The ungual resembles Allosaurus and Torvosaurus more than Baryonyx or Afrovenator. Carcharodontosaurid mani are poorly known and I lack figures of (?)Szechuanosaurus campi and Szechuanosaurus zigongensis. The pedal ungual resembles sinraptorids and carcharodontosaurids more than Allosaurus, but may be coelurosaurian. Thus, I would say the material is probably carnosaurian , but unassignable to a family until more information is available.