| Patagosaurus | |
|---|---|
.jpg) | |
| Restored skeleton with reconstructed skull,Museo Argentino de Ciencias Naturales | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | †Sauropodomorpha |
| Clade: | †Sauropoda |
| Family: | †Cetiosauridae |
| Genus: | †Patagosaurus Bonaparte1979 |
| Species: | †P. fariasi |
| Binomial name | |
| †Patagosaurus fariasi Bonaparte 1979 | |
Patagosaurus (meaning "Patagonia lizard"[1]) is an extinctgenus ofeusauropoddinosaur from the middleToarcian ofPatagonia,Argentina. It was first found in deposits of theCañadón Asfalto Formation, which date to around 178million years ago. Although originally twelve specimens were assigned to the taxon, at least one of them may belong to a different genus.Patagosaurus probably lived alongside genera such asPiatnitzkysaurus,Condorraptor, andVolkheimeria.
SincePatagosaurus is known from many specimens, including at least one juvenile, its anatomy and growth are fairly well understood. Both ages exhibit the typical features of a sauropod: a long neck, small head, a long tail, andquadrupedal stance. The juvenile exhibits features different from the adult in regions like themandible,pectoral girdle,pelvis, andhindlimb, although overall their anatomy is quite similar. The many known specimens help fill in gaps in the anatomy of the genus, such as the forelimb and skull. Parts of the skeleton, like the pectoral girdle,tibia, andpubis are more robust, while others, like theforelimb andischium, are more gracile. The material ofPatagosaurus is similar to closely related taxa likeCetiosaurus andVolkheimeria, moreprimitive genera such asBarapasaurus andAmygdalodon, and morederived sauropods likeDiplodocus andCamarasaurus.
In the 1970s many specimens of a previously unidentified dinosaur were found associated together in the same bed and locality: a pebbly stratum near a route toCerro Condor.[2] The specimens were first described byJosé Bonaparte in1979. For the fossil he erected the genusPatagosaurus, as well as itstype speciesP. fariasi.[3] The generic name ofPatagosaurus comes from the location of its find in Patagonia, and the fact that it is a reptile.[1] Thespecific name honours Ricardo Farias, on whose land the initial discovery was made. The genus was originally known from an almost complete postcranial skeleton lacking a skull as theholotype, and many referred specimens;[3] however, in 2003 it was found that a dentary was referable to the species, so more specimens are probably this taxon.[4] Its skeleton was found near those ofPiatnitzkysaurus andVolkheimeria in the layers originally suggested asCallovian- toOxfordian-agedPatagonian deposits of theCañadón Asfalto Formation.[4] These layers have been recently re-dated, finding out thanks to advanced zircon datation that the bones of the three genera and all the vertebrates of Las Charcitas member where deposited in between 179 and 178 million years, that is Middle-Late Toarcian.[5]Patagosaurus is almost completely known with many articulated specimens found covering almost all of the skeleton, including parts of the skull.[2] Over twelve specimens have been referred to the species,[1] although some of the material is probably from a unique taxon.[4] Bonaparte (1986) assigned three specimens other than the holotype PVL 4170, PVL 4076,MACN CH 934 and MACN CH 933 to the genus. While the holotype includes a postcranial skeleton, the others are known from cranial material and a nearly complete juvenile skeleton and skull.[2][4] MACN CH 933 is directly comparable with the type material ofPatagosaurus, which confirms its association with the genus. A specimen first referred toPatagosaurus in 2003, MPEF-PV 1670 (which includes just a lower jaw), is also very similar to MACN CH 933, and differences can be associated with age, so therefore, MPEF-PV 1670 presumably represents adult cranial material. However, the teeth of MACN CH 934 are very different from those of both lower jaws (MACN CH 933 and MPEF-PV 1670), so it can be identified as another sauropod from the same deposit asPatagosaurus. Thus, the taxon only certainly includes PVL 4170, MACN CH 933 and MPEF-PV 1670.[4]
Patagosaurus is a sauropod that possessed a general and unspecializedbauplan of beingquadrupedal, having an elongate neck, a small head and a very long tail. Therefore, it is similar toCetiosaurus and other related genera, who possessed the samemorphology. It has been estimated that it was about 16.5 m (54 ft) long and weighed about 7.88 tonnes (7.8 long tons; 8.7 short tons).[6] An earlier estimate byJohn S. McIntosh and his colleagues in 1997, found thatPatagosaurus was approximately 15 m (49 ft) long, and also 9.44 metric tons (9.3 long tons; 10.4 short tons) in weight,[7] similar to the later estimates by Holtz.[1] A 2006 study byDonald M. Henderson calculated the weight ofPatagosaurus to be 7.89 t (7.8 long tons; 8.7 short tons), a smaller estimate than McIntosh's.[8]
The skull ofPatagosaurus is not very well known, with a 2003 revision byOliver Rauhut determining only a few jaws are certainly referrable to it, as opposed to nearly the entire skull. MPEF-PV 1670 shows what the morphology of the adult or subadult skull was like, while MACN CH 933 represents a juvenile individual. Based upon howbroad,high and short the adult articulatedmandibles ofPatagosaurus are, its snout would have been short, high and broad as well, a typical feature of most sauropods.[4]
The teeth ofPatagosaurus are reminiscent of morederived sauropods. They are similar in morphology toEuhelopus, being concave on one side as well as havingcrowns with fairly great expansions. They are also similar toCamarasaurus, although the latter genus has less of a concavity and expansion.[9] The teeth also possess marginal denticles on the crown.[4][9] Based on histological studies, an individual ofPatagosaurus would have replaced a tooth every 58 days, similar to 62 days forCamarasaurus, and 34 days forDiplodocus.[10]
Most of the postcranial skeleton is known inPatagosaurus. Thecervical,caudal anddorsal vertebrae are generally similar toCamarasaurus, although thesacrum possesses many distinct features. The sacrum is well preserved, showing thatPatagosaurus possessed five sacral vertebrae. All the vertebrae but the fifth are fused together. All theneural spines are tall, and thecentra are occasionallytransversely narrow. Theneural canal of the vertebrae is unique among sauropods, however. Starting from the very end of the first vertebra, and extending to almost the end of the third there is an enlargement of the canal, forming a well-defined cavity. Even though the sacrum itself is distinguishing, its sacral ribs resembleCamarasaurus. The sacral vertebrae have a total length of 540 mm (21 in), with the total sacral length being 920 mm (36 in).[2]
Thepelvic girdle is well preserved and well studied. In the holotype, the pelvic girdle is almost complete, only lacking theproximal ends of eachischium. Theilia of the holotype are well known, and show many distinct features. The pubic peduncle, where the ilium articulates with the pubis, is long and straight and has an expansion on the end, as in many sauropods. The upper edge of the iliac blade is curved and thick, with rugosities (rough spots) for cartilage attachment. The pubic elements are large and robust in adults, more so than in juveniles. They are flat when viewed from in front, andconvex when seen from behind.Lapparentosaurus resemblesPatagosaurus when comparing their pubes. The ischia are much more gracile than the pubes, and only have a smalldistal expansion. While the ilia resembleBarapasaurus, and the pubes resembleLapparentosaurus, the ischia are most similar toDiplodocus andApatosaurus.[2]
The hindlimbs ofPatagosaurus are based on scant material, somefemora, atibia and a few nondescriptpedal bones. Two femora come from an adult, with a single additional bone known from the juvenile. The adult femora are proportionately different from the juvenile, being mostly straighter and moreovoid in cross-section. Thefemoral head is well preserved, although lacking thegreater trochanter.[11] The distal end is rather symmetrical when viewed from behind, with two similarly sizedcondylar surfaces. In the juvenile, thefourth trochanter is completely in the proximal end. The tibia has a well-developedcnemial crest, and is also short and robust. The surface that would have articulated with theastragalus in life has theanterior half raised, and theposterior half lowered.[2]
Thepectoral girdle is well known. Both the left and rightscapulae andcoracoids are known, though incomplete. The scapulae are large and robust, and thicken as they near the glenoids. The scapular blades are flat, although they are both convex along the anterior edge. Where the scapulae and coracoids articulate, the coracoids are thickest, and they become gradually thinner as they gain distance from the scapulae. The younger specimen ofPatagosaurus possesses a slightly different morphology of the pectoral girdle, with slightly differing proportions, such as a slightly smaller scapular blade. The coracoids resembleBarapasaurus in shape, and differ fromCamarasaurus, although they cannot be directly compared with those ofCetiosaurus.[2]
The forelimbs ofPatagosaurus are only based on three bones from the juvenile specimen, and nomanual elements are preserved. Thehumeri are slender and elongate, lacking great proximal and distal expansions. The incompletedeltoid crest, only shows that it was wide, and likely had a projection below and behind. Like the humeri, theradius is slender, and lacks large expansions on either end. On the edge closest to theulna, the radius possesses a ridge along its edge, which corresponds to whereradioulnar ligaments would have attached. The ulna is complete, although sediment-filled breaks might have altered its original shape. The forelimb ofPatagosaurus is much moregracile and different from the robust later sauropods likeCamarasaurus andApatosaurus, and instead resembles moreDiplodocus.[2]
When originally described,Patagosaurus was identified as a relative ofCetiosaurus in the familyCetiosauridae. It can be distinguished fromCetiosaurus, a similar genus, by features of the ischium and vertebrae. Another genus also identified as a cetiosaurid by Bonaparte,Volkheimeria, was named in the same paper asPatagosaurus. Features uniting the genera were identified in the pelvic structure and vertebrae, specifically the caudal neural spines and the ilium and ischium. These characteristics show that the genera are more derived thanAmygdalodon, yet moreprimitive thanHaplocanthosaurus.[3]
Later in 1995,Paul Upchurch published a paper on early sauropods, findingPatagosaurus as a cetiosaurid again. He found that although earlier works had distinguished two groups, the shunosaurines and cetiosaurines, in the family, but thatShunosaurus and relatives were actually closer toEuhelopus, and cetiosaurines (Cetiosaurus,Patagosaurus andAmygdalodon) were the only true cetiosaurids. Upchurch noted, however, that further work on the group might reveal different conclusions.[12]
In a 2009 revision ofEuhelopus,Jeffrey A. Wilson and Upchurch published a joint analysis on primitive eusauropodan relationships. They found thatPatagosaurus was in fact not a sister taxon ofCetiosaurus, but instead more basal than the genus, effectively invalidating Cetiosauridae.[13]
A 2021 study foundPatagosaurus to be a member of Cetiosauridae.[11]
| Sauropoda |
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Successivephylogenetic analyses from 2020, 2021, and 2024 have confirmed a close relationship betweenBagualia,Nebulasaurus,Patagosaurus, andSpinophorosaurus. The results of Gomez et al. (2024) are shown in thecladogram below:[14][15][16]
Patagosaurus was uncovered in the JurassicCañadón Asfalto Formation, originally thought to be Middle or Late Jurassic, but found recently to be Late Early Jurassic (Middle Toarcian) in age.[5] The Chacritas Member hosted and hypersaline and alkaline lake similar to modernLake Magadi inKenya, while nearby environments where developed in a similar way to modernWaimangu Volcanic Rift Valley of New Zealand, with nearby volcanic influence of the Chon Aike ProvinceThe holotype of Manidens comes from the Chacritas Member of theCañadón Asfalto Formation. This member is mostly made of two major depositional settings: lacustrine and fluvial deposits, that have intervals of tuffaceous materials, suggesting this environments coevolved with volcanic activity.[17] Palustrine littoral environments levels are seen at Cerro Cóndor and Estancia Fossati, characterized by the presence of lacustrine limestones interbedded with shales, tuffs and sandstones.[18] The lacustrine section has been called the "Chacritas Paleolake", and seems to have been a rather saline or even hypersaline hydrologically closed pan lake, shallow in deep, with marginal zones and palustrine subenvironments made of low-energy ramp-like margins.[19][20] This unit preserves a large variety of flora and fauna.[21] Directly below the formation is a layer of ash, indicating a nearbyvolcano.[21] Floral composition was made ofLycophytes,Equisetales,Ferns,Conifers,Bennettitales andPeltaspermales, all along abundance of charcoal particles, suggest frequentWildfires and/orForest fires. Deep lacutrine bodies show abundance ofCharales.[22] The fauna is dominated by tetrapods, ranging fromaquaticamphibians toterrestrialturtles,mammals anddinosaurs. The sole amphibian known isNotobatrachus; turtles are represented by a distinct form that was namedCondorchelys; mammals are known from a few genera, includingArgentoconodon,Asfaltomylos andHenosferus; multiple dinosaurs have been identified, including the HeterodontosaurManidens,[23] sauropodsVolkheimeria,Bagualia,Patagosaurus and a few other genera, andtheropods include the relatedPiatnitzkysaurus andCondorraptor, as wellAsfaltovenator &Eoabelisaurus.[21][24]
Despite coexisting with multiple other sauropod taxa,Patagosaurus was able to avoid direct competition with them, as its tooth morphology differed substantially from coeval sauropod taxa, a feature indicative of significant dietary niche partitioning in its ecosystem.[25]
