At last! Some sauropods enter the LRT.

Overlooked no longer: the clade Sauropoda.
Learning about clade members now for the first time. Three have been added to the large reptile tree (LRT, 1291 taxa): Diplodocus, Camarasaurus and Brachiosaurus (Figs. 1, 4).

Figure 1. Several sauropod skulls to scale with DGS colors on the bones. Here are Shunosaurus, Camarasaurus, Brachiosaurus and Diplodocus.

Figure 1. Several sauropod skulls to scale with DGS colors on the bones. Here are Shunosaurus, Camarasaurus, Brachiosaurus and Diplodocus.

Note:
the antorbital fossa is absent in derived taxa.

Figure 2. Family of Brachiosaurus illustration from A Dinosaur Year 1989.

Figure 2. Family of Brachiosaurus illustration from A Dinosaur Year 1989 (flipped left to right). The original illustration hangs on the wall behind my computer monitor.

Note 2:
The palate of sauropods shows an increasing space allotted to the internal nares. That makes sense given the increased volumes of air passing in and out of the nares of these increasingly gigantic dinosaurs — a volume that has to be several times the volume of the dead air in that long sauropod throat.

Figure 3. Sauropodiform and sauropod palates, Yizhousaurus, Diplodocus, Camarasaurus and Brachiosaurus. The choanae (internal nares) get bigger in sauropods.

Figure 3. Sauropodiform and sauropod palates, Yizhousaurus, Diplodocus, Camarasaurus and Brachiosaurus. The choanae (internal nares) get bigger in derived sauropods.

Other sauropod traits:

  1. Fingers reduced to single phalanx stubs below semi-tubular metatarsals. Only digit 1 retains an ungual and tracks show it was retroverted, dorsal side down, saving the point, oriented medially to posteriorly (Fig. 4).
  2. External nares dorsal with fragile to absent premaxillary ascending process (Fig. 1).
Figure 5. Reconstructions of manus and pes of Camarasaurus SMA0002 from Tschopp et al.

Figure 4. Reconstructions of manus and pes of Camarasaurus SMA0002 from Tschopp et al. 2015.

The LRT
divided dinosaurs into theropods and phytodinosaurs in 2011. Sauropodomorpha is a phytodinosaur clade, the sister clade of the clade Ornithischia (Fig. 5). Currently 5 taxa within the Phytodinosauria precede this split.

Figure 4. Subset of the LRT focusing on the Phytodinosauria. Three sauropods are added here.

Figure 4. Subset of the LRT focusing on the Phytodinosauria. Three sauropods are added here.

More
on each of these sauropods will come shortly.

References
Tschopp E, Wings O, Frauenfelder T, and Brinkmann W 2015. Articulated bone sets of manus and pedes of Camarasaurus (Sauropoda, Dinosauria). Palaeontologia Electronica 18.2.44A: 1-65.

4 thoughts on “At last! Some sauropods enter the LRT.

  1. Yet again, DGS fails. You gave Camarasaurus and “Brachiosaurus” (= Giraffatitan) weird short surangulars that no(?) dinosaur has. Just check figure 47 of Janensch (1935) or e.g. fig. 1 in Gilmore (1925), fig. 18 in McIntosh et al (1996), etc.. The orange and purple are the same bone, with just a bit of articular visible by the jaw joint.

    • Yet again, you come to my rescue! Let me remind you, it’s not the DGS that fails…because every other bone suture was recovered correctly, as you indicate by your silence. It was operator error. I should have known better. Thank you for your help. Let’s work on that tendency to blackwash.

      • My silence was due to limited time and energy. I just noticed the surangulars as obvious errors. Based on Janensch (1935- fig. 56; 1936- plate IX fig. 1-2) in ‘Brachiosaurus’…
        – The nasal descending process includes your upper segment of the maxilla ascending process.
        – No part of the premaxilla ascends the posteroventral nasal edge.
        – The anterodorsal corner of the lacrimal was considered part of the nasal by you, the lacrimal forks dorsally.
        – You didn’t color the ventral tip of the postorbital that curves anteriorly.
        – You didn’t color the anteroventral parts of the quadratojugal or quadrate, and colored the anterior edge of the dorsal quadratojugal process as part of the quadrate.
        – The frontoparietal suture should be over the ventral postorbital process.
        – You didn’t color the anterior frontal (projecting anterodorsally).
        – You have the anterior part of the squamosal as part of the parietal.
        – The posteroventral dentary process bifurcates, the dorsal portion being colored as surangular by you.
        – The posterior angular-surangular suture is below that lit horizontal area you color as part of the angular.
        – The posterodorsal tip of the retroarticular process you have colored as the articular is still the surangular. The articular is only visible as your uncolored dorsal bump by the jaw joint.

        So no, every other bone suture was not recovered correctly. Your DGS reconstructions are generally like this with a lot of little mistakes and a few doozies. Also note that some portions are broken (e.g. ventral squamosal process) so that the original structure is larger than your coloring, and that the two sides differ in some characters (e.g. the jugal contacts the aof on the other side; yours is the right side reversed). You should really get a hold of Janensch’s papers if you haven’t already.

      • Thank you for the nips and tucks. The skull is quite cracked here and there. I did not consult the original text, nor my sculpture to scale based on the original text, nor did I put a lot of effort into this particular tracing based on a photocopy from the 1980s. Your attention to detail is greatly appreciated.

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