2009 Portland GSA Annual Meeting (18-21 October 2009)
Paper No. 172-15
Presentation Time: 9:00 AM-6:00 PM

RANCHO LA BREA MASTODONS, ARE THEY SMALLER THAN MAMMUT AMERICANUM FROM ELSEWHERE IN THE UNITED STATES?

TRAYLER, Robin B., Department of Earth and Environmental Sciences, California State University, Fresno, CA 93740, robintrayler@csufresno.edu and DUNDAS, Robert G., Department of Earth & Environmental Sciences, California State University, Fresno, CA 93740

Rancholabrean records of Mammut americanum are common in California, with over 100 reported localities. Most specimens are dental remains representing single individuals. Among the few sites preserving multiple individuals is Rancho La Brea. Miller (1987) and Harris (2001) reported that Page Museum Rancho La Brea mastodons are smaller than other North American specimens but neither author provided supporting evidence. We examined Rancho La Brea mastodon specimens in the University of California Museum of Paleontology (UCMP) to evaluate the previous statement about Mammut size.

UCMP 198852 and 198861 are partial right dentaries. UCMP 198852 M3 width is 83.0 mm and length is 199.7 mm. UCMP 198861 has an M1 and M2. M1 width and length are 66.5 mm and 108.5mm, respectively. The M2 width is 79.1 mm and length is 110.5 mm. Age is estimated to be 34-39 and 20 years, respectively. UCMP 198853 and 198858 are partial left dentaries. The M3 of UCMP 198853 is 83.1mm wide and 190.0 mm long. UCMP 198858 has a broken M2, preventing standard measurements. Tooth wear suggests UCMP 198853 is ~34 years old while the presence of the M1 alveolus in UCMP 198858 indicates an individual greater than 18 years in age. UCMP 198859 is a partial cranium with left and right tusk alveoli. The left alveolus dorsoventral diameter is 86.5 mm and mediolateral diameter is 78.2 mm. The right alveolus dorsoventral diameter is 85.6 mm and mediolateral diameter is 79.4 mm. UCMP 198860 is a partial cranium with right M1 and M2. M1 width is 69.9 mm and length is 97.1 mm. M2 width is 74.9 mm and length is 97.2 mm. The individual is estimated to be ~20 years in age.

UCMP Rancho La Brea mastodons have long, narrow teeth compared to Trolinger Spring and Boney Spring mastodons from Missouri and Utah specimens. The M3 of UCMP 198852 and 198853 are the most pronounced examples. The M1 and M2 of UCMP 198861 and M1 and M2 from 198860 are small compared to Missouri specimens. The M3 of UCMP 198853 and 198852 are similar in width to Utah specimens but are 22 and 32 mm longer, respectively. The M2 of UCMP 198861 is larger than Brigham Young University specimen 4379, while the M2 of UCMP 198860 is about the same length but 5 mm narrower than the aforementioned male specimen from Utah. Further analysis of Page Museum and UCMP Rancho La Brea specimens and comparison to other North American Mammut populations is warranted.

2009 Portland GSA Annual Meeting (18-21 October 2009)
General Information for this Meeting
Session No. 172--Booth# 105
Paleontology: Morphology, Systematics, & Education (Posters)
Oregon Convention Center: Hall A
9:00 AM-6:00 PM, Tuesday, 20 October 2009

Geological Society of America Abstracts with Programs, Vol. 41, No. 7, p. 454

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