SAUROPODOMORPHS

Sauropodomorph ancestry is close to that of theropods; they were the first dinosaurs to become quadrupedal, and then dramatically larger and more derived. According to Sereno (1999) only a few synapomorphies unite sauropodomorphs; among these are enlarged nares (= small head) and the longest pedal ungual is in the first toe (hallux).

Sauropodomorph synapomorphies after Langer et al. (1999)

PROSAUROPODS (TEXT, Chapter 15) Sixteen genera are known, evidently comparable to (slightly less than) hadrosaurs in diversity. They were the most abundant large terrestrial animals for 50 myr (through late Triassic and early Jurassic time, Upchurch 1997).

Prosauropods are comparable to, but somewhat smaller in size than hadrosaurs (2.5 - 11 m long, up to 2 mt)

Completely known taxa:

Plateosaurus

Massospondylus

Anchisaurus

Yunnanosaurus

Lufengosaurus

Riojasaurus

Saturnalia Carnian of Brazil, body 1.5 m long (Langer et al. 1999) Azendohsaurus Carnian of western High Atlas; muzzle from skull 20 cm long, body 3 m long

Plateosaurus 4 bonebeds (latest Triassic)

Heavy animals mired in seasonally wet muds (juveniles spared, high weight bearing of feet, high natural selection) Massospondylus Early-middle Liassic, femoral rings indicate maturity in 15 years, 300 kg, rather slow growth rate, indeterminate Evolution in prosauropods: Eoraptor Prosauropods

- head large relative to neck - head small relative to neck

- ext nares normal * external nares enlarged

- pmx excludes maxilla from * maxilla enters narial margin

nares

- postnarial process of mx - postnarial process of mx

triangular triangular to narrow and erect

- anterior teeth leaf-shaped - posterior teeth leaf-shaped

- 4 pmx, 18 mx teeth (small size) - 3-6 pmx, 11-30 mx teeth

- mx teeth to center orbit - mx teeth to antorbital process

- 8 cervical vertebrae, centra - 10 cervical verts, centra

short (no pleurocoels) long (no pleurocoels)

- cervical ribs robust - cervical ribs delicate

- 16 dorsal vertebrae - 15 dorsal vertebrae

- about 45 caudals? - about 50 caudals

- manus ungual I small - manus ungual I enlarged

- manus IV with 1 phal * manus IV with 1-3 phal

- manus V with no phal * manus V with 0-2 phal

- pubis broad laterally * pubis narrow laterally

- tibia longer than femur * tibia shorter than femur

- ischium tapers distally * ischium expands distally

- pes V with 1 phal - pes V with 0-1 phal

In Saturnalia

Which came first, Eoraptor or prosauropods?

Eoraptor apomorphies:

Prosauropod apomorphies Three major varieties (TEXT, Upchurch 1997. Enc. Din.)

Thecodontosauridae (small)

Plateosauridae (medium)

Melanorosauridae (large)

Melanorosaurids parallel the later sauropods in:

Riojasaurus 2-7 m long, Norian melanorosaur (Bonaparte 1995, Ameghiniana 32: 341-349; Upchurch 1997) Why prosauropods are sister group, not ancestors, of sauropods; apomorphic characers: Prosauropod apomorphies barring them from ancestry of sauropods (Upchurch 1997) Benton et al. 2000 (JVP 20 (1): 77-108) regard prosauropods as a clade rather within, rather than a series of outgroups of the sauropoda.

The Oldest Sauropod? (Buffetaut et al. 2000. Nature 407: 72-74)

Isanosaurus: one cervical, one dorsal and 6 caudals, neural spine of one posterior dorsal, two chevrons, one scapula and one sternal plate, and one femur ? latest Triassic of Thailand.

Peculiarities include the very short vertebrae, upwardly oriented femoral head and expanded distal end of femur

There are no skeletal parts preserved which would show prosauropod apomorphies. But it does look like an archaic, abbarent sauropd.
 

SAUROPODS Quadrupedality is achieved with increase in size, cf. from prosauropods weighing 300 kg at the base of the Jurassic to animals weighing on the order of 50 mt within 25 myr.

A small sauropod is 15 m long and weighs 12 mt; few dinosaurs are larger.

Gigantic sauropods (Paul 1997, Dinofest International Proceedings, Acad. Nat. Sci. Philadelphia):

Anderson et al. 1985 (J. Zool., London 207: 53-61), Monbaron et al. 1999 (C. R. Acad. Sci. Paris 329: 519-526), Rich et al. 1999 (Natl. Sci. Mus. Tokyo Monographs 15: 61-84), McIntosh et al. 1996 (Bull. Gunma Mus. N. H. 1)

Brachiosaurus: 29 mt

Cf = 730 mm, Ch = 654 mm; ratio = 1.1162

Opisthocoelicaudia: 22 mt

Cf = 680 mm, Ch = 565 mm; ratio = 1.2035

Atlasaurus: 22.5 mt (Bathonian-Callovian)

Cf = 690 mm, Ch = 565 mm; ratio = 1.2212 Tehuelchesaurus: 31.5 mt (Callovian or earlier)

Cf = @805 mm, Ch = 615 mm; ratio = 1.3089

Apatosaurus: 35 mt

Cf = 845 mm, Ch = 629 mm; ratio = 1.3434

Camarasaurus: 19.5 mt (CM 11393)

Cf = @689 mm, Ch = 502; ratio = 1.3725

Av. Cf/Ch = 1.26, sd = 0.0973

Camarasaurus: 1.6 mt

Cf = @268 mm, Ch = @207.5; ratio = 1.2916

Camarasaurus: 9.3 mt

Cf = 514 mm, Ch = 394; ratio = 1.3046

Camarasaurus: 15.7 mt

Cf = 630 mm, Ch = 472; ratio = 1.3347

Camarasaurus: 19.5 mt (CM 11393)

Cf = @689 mm, Ch = 502; ratio = 1.3725

Camarasaurus alenquerensis: 26 mt

Cf = 785 mm, Ch = 547 mm; ratio = 1.4351

Av. Cf/Ch = 1.35, sd = 0.0579

Wq = 0.078 Ch+Cf exponent 2.73 +/- 0.09

Wb = 0.16 Cf exponent 2.73

Gara Samani humerus 96 cm + in length, Ch = 716 mm

Cf = Ch x 1.27 (Anderson et al. 1985, table IV)

Cf = 911 mm

Largest sauropod Cf:

Sauropod eye: sclerotic plates - Brachiosaurus 70 mm, Diplodocus 55 mm, Nemegtosaurus 73 mm - only hadrosaurs have larger eyes.

The name Brontosaurus - first restoration by Marsh (1883), first mount in AMNH (1905), a primary effect was an enlargement of Museum galleries

Completely known taxa:

Camarasaurus

Shunosaurus

Diplodocus

Apatosaurus

Brachiosaurus - east African specimens not fully mature

Comparison of Diplodocus, TEXT: fig. on p. 346, with Plateosaurus TEXT, fig. on p. 321 (* = weight related character):

"Elephant analogues" or "Parelephants"

Definition of Sauropods: Combination of Upchurch 1998. (Zool. J. Linn. Soc. 124: 43-103), and Wilson and Sereno 1998. (JVP 18, suppl. No. 2, SVP Mem 5, 68 p.):

No information in the diagnosis pertains to the skull, neck, back or shoulder girdle. These parts are not preserved in type skeleton of the heretofore most primitive sauropod, Vulcanodon, from the early Jurassic of South Africa, which has (Upchurch 1995): Tooth to tooth occlusion, as evidenced by flat wear facets on the teeth, is also diagnostic of early sauropods (Barrett 1999, JVP 19 (4): 785-787).

EUSAUROPODA ("TRUE SAUROPODS") fide Upchurch 1995 (Phil. Trans. Roy. Soc. London, Ser. B, 349:365-390), see Sereno 1998, Upchurch 1998 for more details

Characters known to be advanced over basal sauropods (Upchurch 1998):

Cranial characters which may be present in basal sauropods: Postcranial characters which may be present in basal sauropods: CLASSIFICATION OF SAUROPOD SUBGROUPS HAS BEEN VERY UNCERTAIN Incompleteness of material: about as much morphology as a mouse skeleton, but takes years to collect and prepare

Skeletal problems

Sedimentological problems (Hunt et al. 1994, Gaia 10: 261-279) Resulting record (see also Hunt et al.): Shunosaurus 5 skeletons with skulls

Camarasaurus 5 skeletons with skulls

Apatosaurus 1 skeleton with skull

Homoplasy: Russell and Zheng 1993 (Can. J. Earth Sci.) 9 taxa, 21 characters, consistency index 0.59, 6% matrix question marks

Calvo and Salgado 1995 (Gaia 11: 13-33) 15 taxa, 49 characters

consistency index 0.66, 21% matrix question marks

Upchurch 1994 (Gaia 10: 249-260) 32 taxa, 174 characters

consistency index 0.63

Wilson and Sereno 1998: 10 taxa, 109 characters

consistency index 0.81, 22% matrix question marks

Upchurch 1998: 26 taxa, 205 characters

consistency index 0.55, 46% matrix question marks

Differences between Wilson and Sereno (WS), and Upchurch (U):

Euhelopus

Haplocanthosaurus Similarities between Wilson and Sereno and Upchurch:

Sauropods are divided into two major groups: Diplocomorphs and camarasauromorphs; titanosauromorphs are now recognized as camarasaur derivatives by both Wilson and Sereno, and by Upchurch.

CAMARASAUROMORPHS (Camarasaurus + Titanosauriformes of Wilson and Sereno, Brachiosaria of Upchurch), characters selected from both references

TITANOSAUROMORPHS (Somphospondyli of Wilson and Sereno, Titanosauroidea of Upchurch), characters selected from both references DIPLODOCOMORPHS (Diplodocoidea of Wilson and Sereno, Upchurch) CAMARASAUROMORPHS

Giraffe sauropods, morphology closer to that of Plateosaurus than in case of diplodocomorphs; bush, tree browsers, riparian habitats

Includes Euhelopodidae, Brachiosauridae, Camarasauridae, example Brachiosaurus

Atlasaurus ? a primitive brachiosaur-like camarasauromorph from the middle Jurassic of Morocco (Monbaron et al. 1999. C. R. Acad. Sci. Paris 329: 519-526).

Joberia ? a primitive camarasaur-like camarasauromorph from the early Cretaceous of Niger (Sereno et al. 1999. Science 286: 1342-1347)

Also Sauroposeidon, from the middle Cretaceous of Oklahoma, based on elongated neck vertebrae of a giant, late brachiosaur (Wedel et al. JVP 20 (1): 109-114).

Euhelopodidae (formerly thought to be restricted to middle Jurassic-early Cretaceous of Central Asia, now with a possible record in Argentina ? see Rich et al. 1999)

DIPLODOCOMORPHS (whip tailed sauropods)

Most derived sauropods, easy to identify, vacuum-cleaners, pivoting on hind limbs, fern browsers

Includes Diplodocidae, Nemegtosauridae, Dicraeosauridae (for details see Upchurch 1995, 1998)

Basal diplodocoid(?): Shunosaurus (restricted to middle Jurassic of China) DICRAEOSAURIDAE Apatosaurus grew to large sub-adults in about 10 years (Curry 1999 JVP 19 (4): 654-669); Janenschia (a late Jurassic putative titanosaur ancestor) became reproductively adult at ll years ? Sander 2000. Paleobilogy 26(3): 466-488) ? the animal has recently been redescribed by Bonaparte in Palaeontographica.

Diplodocus, 23 m 16 mt

Seismosaurus (Gilette 1991, J. Vert. Paleo 11: 417-433) Amphicoelias (Wilson 1996, J. Vert. Paleo. 16(3): 73A) Cretaceous diplodocoids:

Dicraeosauridae

Amargasaurus cazui (L. Salgado and J. Bonaparte 1991. Ameghiniana 28(3-4): 333-346; L. Salgado and J. Calvo 1992. Ameghiniana 29(4): 337-346); very close to Dicraeosaurus, Late Neocomian of Argentina, cervical spine from Morocco.

Rebbachisauridae (see Sereno et al. 1999. Science 286: 1342-1347).

Rayosaurus agriensis, represented by a superb skeleton described by Calvo and Salgado 1995 Gaia 11: 13-33, Albian-Cenomanian, Argentina (see also Calvo 1999, Natl. Sci. Mus. Tokyo Monogr. 15: 13-45, where it is referred to Rebbachisaurus tessonei, and another specimen as Rayosaurus agriensis, Bonaparte 1996. Dinosaurios de America del Sur, Graficas Sagitaro Iturri, Buenos Aires, 174 p., see p. 108)

Antarctosaurus wichmannianus (Huene 1929. Ann. Mus. La Plata 2(3): 1-196 - see plates 28-29), a primitive member of the Rebbachisauridae, Sereno et al. 1999. Antarctosaurus septentrionalis braincase (Chatterjee and Rudra 1996, Mem. Queensland Mus. 39: 489-532), recently named Jainosaurus (Hunt et al. 1994) Nigersaurus dentary with 600 teeth highly derived, expanded into a broad, squared-off muzzle, diplodocoid position of external nares, scaupula resembles that of Rebbachisaurus (Sereno et al. 1999)

Nemegtosauridae

Nemegtosaurus, skull, Mongolia (Upchurch 1995)

Quaesitosaurus, isolated skull from Mongolia, has quadrate pocket

Both genera are referred to Nemegtosauridae of the Diplodocoidea, Upchurch 1999 JVP 19 (1): 106-125.
 

TITANOSAUROMORPHS ("bird" sauropods)

Includes Titanosauridae, Andesauridae (and Opisthocoelicaudia fide Wilson and Sereno, Upchurch)

Argentinosaurus truly titanic

Saltasaurus neck vertebrae like hadrosaurs

Titanosaurs reviewed by Salgado et al. (1997, Ameghiniana 34: 3-32, 33-48)

Pleurocoelus caudals andesaurian, manus lacks claws

[Antarctosaurus, Nemegtosaurus, Quaesitosaurus all considered titanosaurs; since referred to the Diplodocoidea by Sereno et al.

1999, Upchurch 1999]

Recent Papers on Titanosaurs:

- Argentinosaurus huinculensis, J. Bonaparte and R. Coria 1993. Ameghiniana 30(3): 271-282: giant dorsals with huge zygosphene-zygantra, sacrals and tibia 155 cm long, dorsals 1 m+ high, 50 cm long, huge pleurocoels (Andesauridae with hyp artics; Titanosauridae without hyp artics)

- Ampelosaurus atacis, J. Le Loeuff 1995: C.R. Acad. Sci. (Paris) 321, série IIa, p. 693-699. bone bed occurrence (vertebrae and limb bones, osteoderms) from early Maastrichtian fluviatile sediments, in a vinyard in the Aude Valley of southern France. Animal estimated to be 15 m long

Titanosaurus indicus, Chatterjee and Rudra 1996, Mem. Queensland Mus. 39: 489-532. braincase, parocc proc broad, recurved, basipterygoid processes short

Titanosaurus colberti, Jain and Bandyopadhyay 1997, JVP 17: 114-136. articulated/associated skeleton, no skull parts - a medium-sized animal

Malawisaurus dixei, PhD thesis, Elizabeth Gomani, rhino sized
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