Macronaria
Macronaria is composed of two main
groups: Brachiosauridae and Titanosauria. The brachiosaurids are linked together by unusually long
forelimbs plus cervical verts without split neural spines, while the titanosaurians also have
unsplit cervical neural spines, plus an enlarged sacrum (more verts added
here increases strength to the hip) with another dorsal vert grafted on to give a total of six, teeth
between the pegs of diplodocids and the spoons of the brachiosaurids in form, and
distinctive tail verts cupped on the front end (procoelous). Titanosaurians
were once believed to be close relatives of the diplodocids,
but this is now known to be highly unlikely.
<-- Macronaria
|--Camarasaurus
`--+--Europasaurus
`--Titanosauriformes
|-->Brachiosauridae
`--Somphospondylii
`--+--Euhelopus
`-->Titanosauria
Macronaria: A new macronarian skull is known from the late EK
Cedar Mountain Formation of Utah, and several unnamed macronarians are known
from the EK of Spain. Macronarian remains, including a partial neural arch
and fibula, are also known from the Bajocian (LJ) of India.
Camarasauridae has long been named, but with a
small membership (occasionally including Euhelopus
and company, and/or Aragosaurus and Lourinhasaurus). As possible camarasaurids beyond Camarasaurus are not
particularly well-known, and those that have been added to analyses have not
supported much of a Camarasauridae, there's not much reason to persist in giving
them their own page or heading. Traditionally, they are best represented by LJ
remains from Laurasian continents, although future study may assign some of the
poorly-known macronarians here. Also traditionally (e.g. just Camarasaurus),
they generally had U-shaped troughs splitting
their neural spines, long arms relative to their legs,
robust boxy skulls, and large teeth described as
spoon-like. They were very average in most aspects, and lack the fame of some of
their contemporaries. Camarasaurids appear to have had strongly upwardly-directed
necks.
| Taxon or Taxa: | Time\Place: | Comments: | |
| Camarasaurus: Cope, 1877 (including Cathetosaurus [Jensen, 1988]) | C. supremus (type) Cope, 1877 (?including C. lentus [Marsh, 1889 {originally Morosaurus lentus}]) | Kimmeridgian-early Tithonian (LJ) of Colorado, Utah, Wyoming, and New Mexico | Camarasaurus as a whole was the most
common Morrison Formation sauropod. C. supremus
was
the largest and also latest species, known
from over five partial skeletons and several skulls. The trend of increasing size
over time is seen also in Apatosaurus,
Diplodocus, and possibly Allosaurus. C. lentus was a small, common Camarasaurus species. It is known from at least five skeletons with skulls, including two excellent juvenile specimens. It was essentially the same as C. supremus except for size and possibly the age (possibly from somewhat older rocks). |
| C. grandis (Marsh, 1887 [originally Apatosaurus grandis]) | Kimmeridgian (LJ) of Wyoming, Colorado, and Montana | C. grandis was a common lower Morrison species of camarasaur, currently known from six partial skeletons and two skulls (and numerous other miscellaneous elements). | |
| ?C. lewisi (Jensen, 1988 [originally Cathetosaurus]) | late Kimmeridgian (LJ) of Colorado | First assigned to its own genus, this taxon instead appears to be a very old individual from a Camarasaurus species (although this may change). It was at first reported by its describer that this sauropod was the only sauropod capable of rearing up on its hind legs. Its ilium was angled up in an unusual fashion. | |
| Europasaurus holgeri Mateus, Laven, and Knötschke vide Sander, Mateus, Laven, and Knötschke 2006 |
Kimmeridgian (LJ) of Germany | This is a dwarf macronarian from what were
the islands of Europe (well, probably just one particular island, given
how speciation happens on islands). It is known from 11 individuals
of different ages and sizes (1.7-6.2 m long), and bone histology indicates
that the large individuals were adults. Much of the skeleton is
known, including at least one gorgeous skull that looks a bit like Brachiosaurus
with a shorter snout and taller nasal arch (I got to see photos in a
poster back at SVP 2004). This makes another case of island dwarfism among dinosaurs, the most famous being Magyarosaurus. |
|
Macronaria i.s.:
| Taxon or Taxa: | Time\Place: | Comments: |
| Abrosaurus dongpoi Ouyang, 1989 | Bathonian-Callovian (MJ) of China | This sauropod is as yet rather obscure. It had a Jobaria-like skull with an unusually high number of teeth, and some split neural spines. Unfortunately, the tail is not known. |
| ?Atlasaurus imelakei Monbaron, Russell, and Taquet, 1999 | ?late Bathonian (MJ) of Morocco | Based on a nearly complete skeleton originally referred to Cetiosaurus mogrebiensis, this animal may be a basal brachiosaurid close to Brachiosaurus's ancestry, or not a member of the Neosauropoda at all. |
| Janenschia robusta Wild, 1991 (originally Gigantosaurus robustus Fraas, 1908) | Kimmeridgian (LJ) of Tanzania | Based on (as the species name suggests) some very robust limb bones and other pieces, this animal may have been a basal titanosaurian or related to Camarasaurus. It was previously described as the earliest known "titanosaurid", because of some referred procoelous tail vertebrae, but more recent study indicates that the actual type material may or may not belong to a titanosaurian. The main issue here is the tendency for this animal to change higher-level grouping with every analysis. |
| ?Jobaria tiguidensis Sereno, Beck, Dutheil, Larsson, Lyon, Moussa, Sadleir, Sidor, Varricchio, G. Wilson, and J. Wilson, 1999 (?"Rebbachisaurus" tamesnensis) | ?Hauterivian (EK) of Niger | This recently-described sauropod is known from the remains of several individuals of differing age, including skulls in some cases, making it one of the most completely-known sauropods (living alongside is what may be an ankylosaurian, a first for Africa). It appears to have either been a very basal macronarian, or more basal than Neosauropoda. It had few specializations, unusual for such a late sauropod. |
Titanosauriformes i.s.: A new basal titanosauriform skull is know from the Cenomanian-Turonian (LK) of Argentina.
| Taxon or Taxa: | Time\Place: | Comments: | |
| Astrodon johnstoni Leidy, 1865 (Pleurocoelus) | Aptian-Albian (EK) of Maryland, ?Texas, and Utah | The Astrodon/Pleurocoelus saga
is long and confusing. Both were named from remains from the Arundel
Formation of Maryland, Astrodon from teeth, Pleurocoelus nanus
from vertebrae considered to be juvenile, and Pleurocoelus altus
from remains thought to be the adult of the latter. It now appears
that only one sauropod is known from the Arundel, and Astrodon (sometimes
seen as Astrodonius or Astrodon johnsoni; I'm not really
sure what's going on with the alternate spelling) has
priority. The various remains indicate something like a
brachiosaurid or basal titanosauriform. Astrodon is also Maryland's state
dinosaur. Despite its loss, Pleurocoelus lives on in random EK fossils from North America, Europe, and Africa. Remains from Texas referred to it include those of a very large animal, possibly something like Sauroposeidon, especially around the famous Glen Rose\Paluxy River trackways, where Acrocanthosaurus was probably its main predator. This Texan material may actually belong to a basal titanosaurian, however (apparently not the same as Paluxysaurus). Some Utah remains may belong to Cedarosaurus. Honestly, one could choose to employ just Pleurocoelus if one so desired, or both Astrodon and Pleurocoelus; I'm going to follow Carpenter and Tidwell's 2005 assessment. |
|
| Dongbeititan dongi Wang, X., You, H., Meng, Q., Gao, C., Chang, X., and Liu, J., 2007 | EK of China | Dongbeititan is the first named Jehol Group sauropod, and is known from a partial postcranial skeleton including girdle bones, verts, and limb bones. It was described as a basal titanosauriform more derived than Euhelopus, Fusuisaurus, and Huangheititan, but less derived than Gobititan and Jiutaisaurus. | |
| Erketu ellisoni Ksepka and Norell, 2006 | late EK of Mongolia | Based on six very elongate cranial cervicals, a sternal plate, and a partial hind limb (tibia, fibula, astragalus, and calcaneum), Erketu was a long but not especially massive sauropod, probably something like Euhelopus. The neural spines are split, and the known part of the neck appears to have been fairly straight. Unexpanded cylindrical teeth may belong to it as well. | |
| Fusuisaurus zhaoi Mo, J., Wang, W., Huang, Z., Huang, X., and Xu, X., 2006 | ?Aptian-?Albian (EK) of China | Fusuisaurus may be the most basal known titanosauriform, and one of the largest EK sauropods (which puts it in decent Sauroposeidon\Isle of Wight company). It is based on material including a left ilium and pubis, distal left femur, many ribs, and anterior caudals. | |
| Huanghetitan: You, H., Li, D., Zhou, L., and Ji, Q., 2006 | H. liujiaxiensis (type) You, H., Li, D., Zhou, L., and Ji, Q., 2006 | EK of China | Based on material including a scapulacoracoid and a sacrum, this new basal titanosauriform was a contemporary of the iguanodontian Lanzhousaurus. |
| H. ruyangensis Lu J., Xu, L., Zhang, X., Hu, W., Wu, Y., Jia, S., and Ji, Q., 2007 | K of China | H. ruyangensis is based on a partial skeleton including 6 sacrals, 10 caudals, and some ribs and chevrons. Its claim to fame is having the deepest body cavity among dinosaurs, based on the ribs (one being about 2.93 m long). | |
| Lapparentosaurus madagascariensis Bonaparte, 1986 | Bathonian (MJ) of Madagascar | Based on juvenile remains once referred to Bothriospondylus, this taxon appears to be very close to, if not a direct ancestor of, Brachiosaurus. It has been suggested that the formation in which it was found was actually LTr in age, which would be very interesting. | |
| Pelorosaurus conybearei (?N.D.) Mantell, 1850 (including "Cetiosaurus" brevis [N.D.] Owen, 1842) | Berriasian-Valanginian (EK) of England | Pelorosaurus is a fairly basic EK ?brachiosaurid,
meaning it is somewhat smaller than its Jurassic counterparts, but overall pretty much the
same. "Cetiosaurus" brevis Owen, 1842, a chimera of Iguanodon and Pelorosaurus material, should technically be the name for this taxon (yes, this should be Cetiosaurus brevis), but because nobody has really used the alternate name much in the last century and a half, and because this would mean that what everyone usually thinks of as Cetiosaurus would need a new name and what everyone usually thinks of as Pelorosaurus would suddenly be called Cetiosaurus (possibly making Brachiosauridae into Cetiosauridae in the bargain, depending on where you put Pelorosaurus), there will be a petition made to suppress C. brevis. |
|
| Ornithopsis hulkei (N.D.) Seeley, 1870 (?Pelorosaurus) | Barremian (EK) of England | Sometimes referred to Pelorosaurus, the material Ornithopsis is based on (two dorsals) is not good enough to be sure. | |
Somphospondylii: I'm sorry, but Somphospondylii is about the silliest-sounding and silliest-looking name I've come across.
| Taxon or Taxa: | Time\Place: | Comments: |
| Euhelopus zdanskyi Romer, 1956 (originally Helopus zdanskyi Wiman, 1929) | ?Kimmeridgian (?LJ) of China (the age is a bit fuzzy, and could be EK) | This used to be one of the more familiar euhelopodids. It is known from a partial skeleton and skull, plus very long arm and shoulder material that may or may not belong. Sometimes it's found with the Eusauropoda, but usually it's near the base of Titanosauria in something called Somphospondylii. Erketu may be closely related. |
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