UNUSUAL SURFACE TEXTURE IN PRESACRAL VERTEBRAE OF THE PACIFIC MASTADON (Mammut pacificus) : A CASE REPORT

1. UNUSUAL SURFACE TEXTURE IN PRESACRAL VERTEBRAE OF
THE PACIFIC MASTODON (Mammut pacificus) : A CASE REPORT
Authors: Kaelen Kay, Alton Dooley PhD, Mathew Wedel PhD

2. This is what a normal mastodon vertebra looks like
Thoracic vertebrae in posterior view
with growth plate removed
External surface of epiphyseal growth plate
Internal surface of unfused epiphyseal growth plate
Thoracic vertebrae in posterior view
with growth plate attached

3. ● An associated series of cervical
and thoracic vertebrae (C1-T1) of
a female Pacific mastodon
(Mammut pacificus) in the
collections of the Western Science
Center (WSC, Hemet, CA)
preserve an unusual porous and
woven texture on the caudal
articular surfaces of the centra.
● Although the individual is small
(max centrum diameter = 14cm),
all epiphyseal growth plates of the
vertebrae are closed, and the
preserved texture does not match
that of an unfused centrum or
epiphysis (see previous slide).
This is what we found at Western Science center...
C2
C3
C5

4. Normal morphology Posterior surface of
variant specimen
Anterior surface of
variant specimen
Thoracic vertebra (different individual),
posterior view
C5 vertebra
posterior view
C5 vertebra
anterior view

5. ● Possible explanations for the
unusual texture:
○ aberrant fetal or post-partum
development
○ infections or degenerative
changes during life
○ decomposition processes
○ unusual fossilization
○ weathering
● Methods:
○ We searched the Western
Science Center in Hemet for
similar texture
○ We searched the literature for
evidence of similar texture
○ Neither Western Science
Center or the literature turned
up evidence of a similar
texture

6. C7 C6 C3
C4
C5 C2
Mammut pacificus skeletal
reconstruction by Brian Engh

7. Review of possible causes
● Infections or degenerative changes during life
○ The evenness of the texture across the caudal articular surfaces, as well as an
absence of osteophytes or degenerative changes in the bone, suggest that the
condition was not overtly pathological
● Decomposition processes, unusual fossilization, weathering
○ Unlikely due to the absence of the texture from other individuals from the same
depositional system and from other parts of the vertebrae in the affected individual
● Aberrant fetal or post-partum development
○ Possibly due to the restriction to the caudal surfaces of the centra
○ Numerous large foramina in the woven bone suggest an unusual pattern of
vascularization
Have you seen anything like this?
● We are still looking for examples of similar conditions in other mammals – if you have
seen anything like this, please let us know!

8. Acknowledgements
We thank Brian Engh (http://dontmesswithdinosaurs.com/) for permission to use his art, Brett Dooley for generating
photogrammetric models of the M. pacificus vertebrae, and the staff of the Western Science Center for assistance
searching the collections for other similar specimens.
References
1. Dooley AC Jr, Scott E, Green J, Springer KB, Dooley BS, Smith GJ. 2019. Mammut pacificus sp. nov., a newly recognized species of
mastodon from the Pleistocene of western North America. PeerJ 7:e6614 https://doi.org/10.7717/peerj.6614
2. Zhao FD, Pollintine P, Hole BD, Adams MA, DOlan P. 2009. Vertebral fractures usually affect the cranial endplate because it is thinner and
supported by less-dense trabecular bone. Bone 44:372-379.
3. Kaplan KM, SPivak JM, Bendo, Ja. 2005. Embryology of the spine and associated congenital abnormalities. The Spine Journal 5: 564-576.