(Santa Maria Formation, Middle- Upper Triassic

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Are Spondylosoma and Staurikosaurus (Santa Maria Formation, Middle-. Upper Triassic, Brazil) the ..... straight shaft with only a little expansion proximally. The.
PalBontologische Zeitschrift

74 (3)

393-423

15 Abb.

Stuttgart, Dezelnber 2000

Are Spondylosoma and Staurikosaurus (Santa Maria Formation, MiddleUpper Triassic, Brazil) the oldest saurischian dinosaurs? PETERM. GALTON, Bridgeport With 15 figures

Kurzfassung: Sl~ondylosonzaabscondit~tnz(Ladin, Mitteltrias) (Carnian, Upper Triassic), one of the oldest dinosaurs, posfehlen bestimmte Merltinale der Dinosauriformes-Dinosauria, sesses autaposnorphies of Dinosauriformes, Dinosauria, Sauriwie ein sigmoidal gebogener Hals mit Epipophysen sowie ein schia, and Herrerasauridae, but it retains certain plesioinorphic distal ansetzender Deltopectoralltan~mauf dem Humerus. Die, characters (subcircular distal end to tibia, ?proximally placed welche vorhanden sind (zusatzliche Zwischenwirbelgelenlte deltopectoral crest. axially unshortened neural spine to sacral 1, ?scapular spine unreduced distally) not present in Heweravom Typ Hyposphen-Hypantrum, drei Salualwirbel, verlangersaurus (Carnian, Ischigualasto Formation, Argentina). Howtes Pubis), ltommen auch bei den Rauisuchia (Crurotarsi, ever, the femur is more derived in the loss of the trochanteric Suchia, Rauisuchiformes) vor. Spondylosonza wird mit Vorbeshelf and reduction of the lesser trochanter (as also occurs in halt zu den Rauisuchidae gestellt. Wie die nach ventrolateral gerichteten Sakralrippen zeigen, stand das Ilium schrag (und some prosauropods). Thc two vertebrae sacium of Sta~trikonicht seilkrecht wie bei den Poposauriden). Sta~trikosa~trz~ssaurus is a plesiomorphic character for Dinosauria (also in pricei, einer der altesten Dinosaurier, besitzt Autapoinorphien other herrerasaurids, German Upper Triassic prosauropod Sellosaui-us graczlis - ?males), to which was added either a der Dinosauriformes, Dinosauria, Saurischia und Herreracaudosacral (e.g. Santa Maria prosauropod Saturrzalia, Sellosauridae, aber behalt bestimmte plesiomorphe Merltmale bei su~ti-US gracilis - ?females) or a dorsosacral (e.g. Ischigualasto (rundliches distales Ende der Tibia, ?proximal ansetzender theropod Eoraptor and prosauropod Riojasaurus). Agrosaurus Deltopectoralkasnm, axial unverltiirzte Donlfortsatze bis zum (Upper Triassic, Durdham Down, England - not Australia) is Sakralwirbel 1, ?distal nicht reduzierte Spina der Scapula), die not a herrerasaurid; it is referred to the prosauropod dinosaur bei Hen-erasaui-us (Carnian, Ischigualasto Formation, ArgenTlzecodontosaurus antiquus (Upper Triassic, Durdham Down). tinien) nicht vorhanden sind. Allerdings ist das Femur starker abgeleitet, weil die Trochanter-Kante verloren ging und der anteriore Trochanter reduziert wurde (was auch bei manchen Introduction Prosauropoden vorkommnt). Die zwei Sakralwirbel \ion Staui-ikosaurus sind ein fiir die Dinosauria plesiosnorphes In 1929, F. VON HUENEof the University of Tiibingen Merltmal (auch bei anderell Herrerasauriden und bei den collected fossil reptiles from the eroded 'sangas' or gul?Mannchen des deutschen Prosauropoden Sellosaui-us lies, that expose the red sediments of the Santa Maria gmcilis). Diesen zwei Saltralwirbeln wurde entweder ein Formation (Middle and Upper Triassic) of the Parana Caudosaltralwirbel hiilzugefiigt (z.B. bei dem Santa MariaBasin, State of Rio Grande do Sul in southern Brazil, the Prosauropoden Saturizalia und bei den ?Weibchen von Sellogeology of which was detailed by VON HUENE& sactrus gmcilis) oder ein Dorsosakralwirbel (wie bei desn Ischigualasto-TheropodenEoraptor und dein Prosauropoden STAHLECKER (1931). Later, VOK HUENE(1942) described Riojasaur~~s). Agi*osa~trus(Obertrias, Durdham Down, Engspecimens of saurischian diilosaurs (Figs. 1,2B-E) from land - nicht Australien) ist ltein Herrerasauride, sondern er wird the lower part of the Santa Maria Formation near the city zu dem prosauropoden Dinosaurier Tlzecoclor~tosa~irus antiof Santa Maria. quus (Obertrias, Durdham Down) gestellt. Abstract: Spondylosoi?za absconclitur?~ (Ladinian, Middle Triassic) lacks certain Di~losauriformes-Dinosauriacharacters (sigmoid curve and epipophyses in neck, distally placed deltopectoral crest on humerus ) and those present (accessary hyposphene-hypantra vertebral articulations, three sacral vertebrae, elongate pubis) also occur in the Rauisuchia (Crurotarsi, Suchia, Rauisuchiformes). Sporzdylosonza is tentatively referred to the Rauisuchidae because, as indicated by the ventrolaterally directed sacral ribs, the ilium was held obliquely (and not vertically as in the Poposauridae). Sta~~rikosaurus pricei

Spondylosoma absconditum VON HUENE1942 is based on well preserved but fragmentary material that includes a tooth, seven vertebrae and a few incomplete girdle and limb elements from the vicinity of ChiniquA (or XiniquB), to the west of the city of Santa Maria (for maps see VON HUEI'JE& STAHLECKER 1931: fig. 1; COLBERT 1970: fig. 1; BARBERENA et al. 1985: fig. 1).The bones were found separately among those of the large dicynodoilt reptile Stalzleclzeria in Excavation 44 at "Bauin-Sanga" (see VON HUENE& STAHLECKER 1931: 39-40 for section). VON

Address of the author: Dr. PETERM. GALTON, College of Naturopathic Medicine, University of Bridgeport, Bridgeport, CT 066012449, USA. 0031-0220/00/0074-0167

S 11.00

O 2000 E Schwe~zelbait'scheVerlagsbuchhandluilg, D-70176 Stuttgart

Fig. 1.- 1-13: Spoizdylosonza abscoi~ditunzfrom Middle Triassic of Brazil: lectotype individual (1-3, 6, 7), paralectotypes (5, 813), and a referred specimen (4), GPIT 479/30/1-13 (from V O N HUENE1942: pl. 30, figs. 1-13). 1: cervical vertebra 4 or 5 in left lateral view (cf. Figs. 5F-K). 2: cervical vertebra 6 or 7 in a: left lateral, b: anterior and c: posterior views (cf. Figs. 4C, 5A-E, 6A). 3: posterior dorsal vertebra in a: left lateral, b: anterior and c: posterior views (cf. Figs. 5L-N, 6B-D). 4: first dorsal vertebra of a large individual in a: left lateral, b: anterior and c: posterior views (cf. Figs. 5 0 , P, 6E-H). 5: partial centrum of a mid-dorsal vertebra in right lateral view (cf. Figs. 5Q, R). 6: sacral vertebra 1 in a: right lateral and b: posterior views (cf. Figs. 5S, 7A-D; 8AD). 7: sacral vertebra 2 in a: right lateral and b: posterior views (cf. Figs. 7A-E, 8E-H). 8: sacral vertebra 3 in a: right lateral and b: anterior views (cf. Figs. 7A-D, F, 81-L). 9: distal half of left scapula in lateral view (cf. Figs. 8M-0). 10: proximal half of right scapula in lateral view (cf. Figs. 7G-J). 11: proximal endof-left humerus in anterip view (cf. Figs. 6L-N). 12: proximal part of right pubis in lateral view (cf. Figs. 9A-D). 13: distal end of left femur in posterior view (cf. Figs. 5T, U, 61-K).- 14: Archosauria, incertue sedis - proximal part of right tibia in lateral view (cf. Figs. 5V-X, 60), GPIT 479/30/14 (from \ION HUENE1942: pl. 30, fig. 14). - Scale bar equals 1 cm.

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Fig. 2. - A: Staui~ikosaui-uspi-icei from Late Triassic of Brazil, MCZ 1669, skeletal reconstruction (proximal part of scapula not (1977). B-E: anterior half of cervical vertebra (GPIT 479/0256b), Archosauria included), total length about 2.1 m, from GALTON iacevtae sedis, from Middle Triassic of Brazil in B: ventral, C: posterior (cross-section of centrum across break), D: anterior and E: right lateral views (cf. Figs. 3A-E), from VON HLENE(1942). - Scale bar equals 1 cm (B-E).

Fig. 3. Archosa~~ria zrzcei-tae sedis from the Middle Triassic of Brazil. A-E: anterior half of a cervical vertebra, GPIT 495/0256b, in A: dorsal, B: ventral, C: posterior, D: anterior and E: right lateral views (cf. Figs. 2B-E). F-H: incomplete large anterior caudal vertebra, GPIT 47910249, in F: right lateral. G: posterior and H: left lateral views (cf. Fig. 4D). - Scale bars equal 1 cm.

HUENE(1942: 247) noted that the name Sl~ondylosorna absconditurn referred primarily to the vertebrae. However, he concluded that the postcranial elements wcrc probably also correctly included for the following reasons: they were found with the vertebrae in fairly close proximity to each other in the same excavation, all the

bones of Sl~onclylosonzaagree in size and preservation, and the only other non-Stahleckel-ia reptilian bone found in Excavation 44 was a large tooth of a cynodont reptile. VON HUENE(1942) referred to Spondylosorna absconditunz another tooth and the distal end of a radius from the adjacent Excavation 45 in the "Baum-Sanga", plus a

larger first dorsal vertebra found with small dicynodonts R e p o s i t o r y a b b r e v i a t i o n s : BRSMG:BristolCityMuand cynodonts in the "Cynodont-Sanga" several kilo- seum and Art Galleries, Museunl of Geology, Bristol; BMNH: meters f~lrtherwest of Chiniquh (see VON HUENB& The Museum of Natural History, London; GPIT: GeologischPaliiontologisches Institut der Universiiat Tiibingen; MCZ: STAI-ILECI