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Caudal pneumaticity and pneumatic hiatuses in the sauropod dinosaurs Giraffatitan and Apatosaurus - PubMed Skip to main page content
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. 2013 Oct 30;8(10):e78213.
doi: 10.1371/journal.pone.0078213. eCollection 2013.

Caudal pneumaticity and pneumatic hiatuses in the sauropod dinosaurs Giraffatitan and Apatosaurus

Mathew J Wedel  1 , Michael P Taylor
Affiliations

Caudal pneumaticity and pneumatic hiatuses in the sauropod dinosaurs Giraffatitan and Apatosaurus

Mathew J Wedel et al. PLoS One. .

Abstract

Skeletal pneumaticity is found in the presacral vertebrae of most sauropod dinosaurs, but pneumaticity is much less common in the vertebrae of the tail. We describe previously unrecognized pneumatic fossae in the mid-caudal vertebrae of specimens of Giraffatitan and Apatosaurus. In both taxa, the most distal pneumatic vertebrae are separated from other pneumatic vertebrae by sequences of three to seven apneumatic vertebrae. Caudal pneumaticity is not prominent in most individuals of either of these taxa, and its unpredictable development means that it may be more widespread than previously recognised within Sauropoda and elsewhere in Saurischia. The erratic patterns of caudal pneumatization in Giraffatitan and Apatosaurus, including the pneumatic hiatuses, show that pneumatic diverticula were more broadly distributed in the bodies of the living animals than are their traces in the skeleton. Together with recently published evidence of cryptic diverticula--those that leave few or no skeletal traces--in basal sauropodomorphs and in pterosaurs, this is further evidence that pneumatic diverticula were widespread in ornithodirans, both across phylogeny and throughout anatomy.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Caudal pneumaticity varies among sauropods.
In the diplodocid Tornieria, the first 15–20 caudal vertebrae have neural arch laminae and fossae, and lateral pneumatic foramina opening into large internal chambers. Images traced from Remes (: fig. 31 [lateral view]) and Janensch (: fig. 7 [cross-section]); the two views are from different vertebrae. In the basal titanosaurian Malawisaurus, caudal pneumaticity is restricted to a handful of proximal caudal vertebrae, in which the neural arches are honeycombed with pneumatic chambers but the vertebral centra are solid. Images traced from Wedel (: fig. 2A [lateral view] and 2C [cross-section]). In the derived titanosaurian Saltasaurus, the first 20–25 caudal vertebrae have large external fossae but small external foramina, and both the neural arches and centra are honeycombed with chambers. Images traced from Powell (: plate 53 [lateral view]) and Cerda et al : fig. 4F [cross-section]); the two views are from different vertebrae.
Figure 2
Figure 2. The phylogenetic distribution of caudal pneumaticity in sauropods and other dinosaurs is complex.
Boxes represent proximal, middle, and distal caudal vertebrae, arbitrarily defined for sauropods as caudals 1–10, 11–20, and 21 on, respectively; blue boxes indicate that pneumaticity is present in that part of the tail. Pneumaticity data for theropods come from Benson et al —note that although Theropoda is collapsed to a single node in this figure, caudal pneumaticity is not primitive for the clade, but evolved independently several times in both non-avian theropods and birds , , . Data from sauropods come from the sources listed in Table 1. The figure also shows the phylogenetic framework we use in this paper. The phylogenetic framework is drawn from Whitlock for diplodocoids, Mannion et al for basal macronarians and Xianshanosaurus, Calvo et al for most titanosaurs, and Campos et al for Trigonosaurus. Basal sauropodomorphs are a grade, not a clade, but they are listed together here for convenience since they all lack caudal pneumaticity.
Figure 3
Figure 3. The caudal vertebrae of ostriches are highly pneumatic.
This mid-caudal vertebra of an ostrich (Struthio camelus), LACM Bj342, is shown in dorsal view (top), anterior, left lateral, and posterior views (middle, left to right), and ventral view (bottom). The vertebra is approximately 5cm wide across the transverse processes. Note the pneumatic foramina on the dorsal, ventral, and lateral sides of the vertebra.
Figure 4
Figure 4. Giraffatitan brancai tail MB.R.5000 (‘Fund no’) in right lateral view.
Dark blue vertebrae have pneumatic fossae on both sides, light blue vertebrae have pneumatic fossae only on the right side, and white vertebrae have no pneumatic fossae on either side. The first caudal vertebra (hatched) was not recovered and is reconstructed in plaster.
Figure 5
Figure 5. Giraffatitan brancai tail MB.R.5000 (‘Fund no’) in left lateral view.
Shading conventions follow Figure 4, with light blue vertebrae having pneumatic fossae only the left side.
Figure 6
Figure 6. The ‘Fund no’ quarry at Tendaguru preserved a tail of Giraffatitan with the vertebrae roughly in order.
The series of caudal vertebrae catalogued as MB.R.5000 and incorporated in the famous mounted skeleton of Giraffatitan are visible near the bottom of the photo. The photo appears courtesy of the Museum für Naturkunde Berlin.
Figure 7
Figure 7. Pneumatic fossae are present only in the second caudal vertebra in several specimens of Giraffatitan.
Caudal vertebra 2 from the MB.R.2921 (‘Fund Aa’) is shown here in right lateral (left) and left lateral (right) views. Small pneumatic fossae (f) are present on both sides of the centrum, but absent in the rest of the tail. The same pattern of pneumaticity is present in MB.R.3736 (‘Fund D’) and, according to Janensch , in the caudal series from the ‘Fund G1’ quarry.
Figure 8
Figure 8. Patterns of caudal pneumaticity in Giraffatitan and Apatosaurus are complex and frequently include pneumatic hiatuses.
Shading conventions follow Figure 4. The intermittent unilateral and bilateral pneumatic hiatuses (i.e., gaps in pneumatization) in Giraffatitan MB.R.5000 (‘Fund no’) contrast sharply with the very restricted pneumaticity in MB.R.2921 (‘Fund Aa’) and the isolated pneumatic features in Apatosaurus YPM 1980. YPM 1980 has the longest pneumatic hiatuses, unilaterally and bilaterally, that we have found to date in any dinosaur.
Figure 9
Figure 9. Pneumatic fossae are present in the proximal caudal vertebrae in many specimens of Apatosaurus.
Here the first part of the tail of FMNH P25112, the mounted Apatosaurus skeleton in Chicago, is shown in left lateral view.
Figure 10
Figure 10. An isolated pneumatic fossa is present on the right side of caudal vertebra 13 in Apatosaurus excelsus holotype YPM 1980.
The front of the vertebra and the fossa are reconstructed, but enough of the original fossil is visible to show that the feature is genuine.
See this image and copyright information in PMC

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References

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Grants and funding

Research for this study was conducted on a field trip sponsored by DFG Research Unit 533: Biology of the Sauropod Dinosaurs; DFG 533 also supported our travel to Germany. The authors thank Martin Sander (University of Bonn) and the organisers and participants of the field trip. The Field Museum of Natural History supported our travel to Chicago. Research at the Carnegie Museum was supported by a grant from the Jurassic Foundation. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

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