| Lohuecotitan | |
|---|---|
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | †Sauropodomorpha |
| Clade: | †Sauropoda |
| Clade: | †Macronaria |
| Clade: | †Titanosauria |
| Genus: | †Lohuecotitan Díez Díazet al., 2016 |
| Species: | †L. pandafilandi |
| Binomial name | |
| †Lohuecotitan pandafilandi Díez Díazet al., 2016 | |
Lohuecotitan is an extinctgenus oftitanosauriansauropoddinosaur which lived during theLate Cretaceous inSpain. The only species known in the genus isLohuecotitan pandafilandi, described and named in 2016.[1]
The fossil remains ofLohuecotitan were discovered in the site ofLo Hueco,Fuentes,Cuenca, which is part of theVillalba de la Sierra Formation.[1] The formation dates from the UpperCampanian to the LowerMaastrichtian, and would have represented a muddy coastal floodplain.[2] The locality was discovered in 2007 during the cutting of a little hill for installation ofthe railway of the Madrid-Valencia high-speed train. More than 10 000 fossils have been collected, almost half of which belong to titanosaurs comprising more than twenty sets of partial skeletons in anatomical connection or with a low dispersion of their skeletal elements.[2] Teeth and braincases were also recovered. The material belongs to at least two distinct types of titanosaur.[2][3] The holotype specimen ofLohuecotitan,HUE-EC-01, is a disarticulated partial skeleton consisting of cervical, dorsal, sacral, and caudal vertebrae, ribs, an ulna, both ischia, a pubis, a femur, a fibula, and a tibia, along with some indeterminate remains.[1]
The name ofLohuecotitan combines a reference to the type locality withtitan (which refers to the Greektitans). The specific name,pandafilandi, is derived from the name of a giant,Pandafilando de la fosca vista, in the novelDon Quixote.[1]The character is named "Pandafilando of theScowl" inJohn Ormsby's translation.
Lohuecotitan was recognized by its describers as having a number of unique characteristics (autapomorphies) not seen in other titanosaurs. In the dorsal vertebrae, the edges of the postspinallaminae extend outwards. In the first several caudal vertebrae, the medial spinoprezygapophyseal and spinopostzygapophyseal laminae respectively connect to the prespinal and postspinal laminae on the bottom surface. In addition, due to the way that the prespinal and postspinal laminae project upwards, the neural spine of the vertebra appears to be V-shaped from the side, and resemble aGreek cross in cross-section. Each middle caudal vertebra has two roughened structures that extend from the top of the back face onto the top surface of the vertebra. Finally, the bottom portion of each half of thehaemal arches in the posterior caudal vertebrae is split fully into twoarticular facets. These traits form a unique combination not seen in other titanosaurs, along with the centrodiapophyseal laminae being widened on the top and bottom edges in the front and middle dorsal vertebrae (as also seen inSaltasaurus), and a rounded protrusion being present between the front and side trochanters of the fibula (also seen inJainosaurus).[1]
A number of the bones ofLohuecotitan were internallypneumatized, including the cervical vertebrae, sacral vertebrae, and ilium. As is common insomphospondylans, the pneumatic fossae on the cervical vertebrae are shallow; this was also the case in the dorsal vertebrae. The cervical and dorsal vertebrae areopisthocoelous; the caudal vertebrae wereprocoelous (a characteristic common inLithostrotia). The seventh and eighth tail vertebrae are fused together; this probably represents apathology. As in othertitanosauriforms, the dorsal ribs are compressed and blade-like. The ulna was robust, and the bottom surface of the tibia was oval-shaped, as is common in titanosaurs.[1]
In2013 Knoll and colleagues tentatively assigned to an unnamed species ofAmpelosaurus,A. sp., a fossil braincase from Lo Hueco.[4] However, in 2019 Knoll et al. finally referred this braincase toLohuecotitan.[5] This assignment is based on the fact that another braincase morphotype from Lo Hueco was found to be associated with a titanosaur skeleton distinct fromLohuecotitan and because none of the very abundant titanosaur postcranial remains of Lo Hueco belong toAmpelosaurus.[5][1][6]The braincase was found to share many features withA. atacis, such as a back of the skull that is flat. The braincase, MCCM-HUE-8741, is small in size overall, with a front-to-back length of 100.8 millimetres (3.97 in), and the maximum width of the left half being 64.3 millimetres (2.53 in). Parts of the bottom half of the braincase are missing. Even though section are missing, the specimen does not appear to have been deformed much, as the left and right halves are not very different.[7]
Twofrontals are preserved. They are each 57.3 millimetres (2.26 in) long and 64.3 millimetres (2.53 in) wide. The upper surface of each frontal is not smooth. One crest runs along the each frontal, and the together the two crests make up theorbital roof. Bothparietals have also been found. The connection between them is marked by a ω-shaped crest. Viewed from the side, the parietal has two extensions. These extensions are not fully preserved, but they would have been on the border of theupper temporal fenestrae in their middle. Each parietal was preserved as 79.6 millimetres (3.13 in) wide. Thebasioccipital ofLohuecotitan is unique as it has anoccipital condyle that is much wider than tall. The occipital condyle has an irregular surface that was probably caused by the loss of the originalcartilaginous covering. The complete braincase was especially low in the skull, and was oriented to the side. The occipital condyle is 28.6 millimetres (1.13 in) wide and 15.8 millimetres (0.62 in) tall.[7] The braincase floor is made by theparabasisphenoid. Theprootic is a tall but not long bone. The basisphenoid is mostly on the side of it, along with thelaterosphenoid, the parietal, and theotoccipital. The length of theprootic from the front to the back is around 10.6 millimetres (0.42 in).[7]
Compared withGiraffititan, the inner ear ofLohuecotitan shows a more basal morphology. That feature is possibly related to a restricted range of possible movements that involve head-turning.[7]
Like inJainosaurus and most other non-avian archosaurs, the hindbrain and midbrain ofLohuecotitan is relatively poorly preserved in theendocast. In contrast with TMM 40435 and a few other taxa such ascf.Cetiosaurus oxoniensis andGiraffatitan, no characteristic "nub" of thecerebellum can be seen. As in TMM 40435 and many other archosaurs, the back of thebrain is especially narrow inLohuecotitan.[7]
Thecerebral region of the brain is separated from the rest of the brain by a distinct compression caused in the endocranial cavity. The rearmost part of the cerebral region of the braincase has a top with a small expansion. This is different fromJainosaurus. However, relatively much larger expansions are known in the diplodocoid sauropodsDicraeosaurus andDiplodocus. In MCCM-HUE-8741, the small opening in the skull roof middle is responsible for a swelling on the endocast that is suggestive of apineal system. It is in the exact position where thepineal gland is expected to have been, between theforebrain and themidbrain.[7]
Thesemicircular canals are contracted, and they are highly curved. The semicircular system of MCCM-HUE-8741 shows also abasal morphology, because the semicircular canals do not attach to each other.[7]
Lohuecotitan was in 2016 recovered as alithostrotiantitanosaur, more derived thanMalawisaurus. Its position among the lithostrotians is supported by the sharp angle of itszygapophyseal articulations. The consensus of the 20 most parsimonious phylogenetic trees recovered is shown below.[1]
More recently Mochoet al. (2019) in a cladistic analysis, recoveredLohuecotitan within Lithostrotia as a sister species of the European speciesPaludititan.[8]
| Lithostrotia |
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In the same year, Gorscak & O'Connor (2019) in their description ofMnyamawamtuka recoveredLohuecotitan as a saltasaurid.[9]
