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Archive for June, 2008

Spring 2008

28 Jun

The Mammoth News

Spring 2008, Volume 16

The Skull Block and Its Hidden Treasures

This spring term we uncovered a large portion of the top side of the skull, the side that was down in the field, and found several intriguing features. After uncovering most of the top surface, we discovered that the skull is relatively complete but collapsed, probably due to compaction after it had been turned upside down some 17,500 radiocarbon years ago. Compaction would have occurred early as deterioration of bone began, probably after it was buried by the wind-blown silt.

We have also exposed on the skull the right cheek bone, fragile and complex bones in the roof area of the mouth, the attachment area for the trunk, and the two ends of the tusks within the skull where the tusks form and grow. The left tusk has remnants of the tusk socket (alveola) attached, but it appears that the alveola had broken and pieces had shifted prior to burial. This suggests that the left tusk may have rotated in the socket due to its own weight as muscle tissue deteriorated. The alveola on the right tusk appears to be more intact. However, we have not yet completely excavated either alveola.

In the top of the skull we have found a hole or conical shaped indentation (about 5 cm across) that possibly was caused by impact from a tusk of another male mammoth. We have yet to completely prepare this part of the skull and get an expert opinion on the hole, but this idea is intriguing – fighting mammoths! This would explain Benny’s demise. Males fought annually, but generally not fatally, for mating privileges. If this hypothesis is confirmed, then we need to make a case for changing Principia’s mascot to a mammoth – the Fighting Mammoths!

We have also enlarged our Pleistocene fauna finds to include a gray wolf – Canis lupus – and possibly another rabbit! Just above the skull, which would have been beneath the skull when they were buried, we uncovered two bones that we knew right away were not mammoth bones. We sent the bones to the Illinois State Museum where Dr. Jeff Saunders’ colleague, Dr. Chris Widga, identified the larger one as part of the lower leg bone (tibia) of a gray wolf. The smaller bone was part of the second smaller lower leg bone (fibula). Perhaps the wolf died while scavenging the mammoth carcass, but before the skull block had been turned over by, perhaps, another mammoth passing by. It is also possible that this wolf was part of a pack of wolves that was bringing down our mammoth, and it was killed by a blow from one of Benny’s tusks or legs. We also found a few small teeth that are currently being identified – possibly another rabbit.

We uncovered the tusk tips for the first time this term and discovered that they are both complete, coming to a tapered end. Careful excavating and repair work were needed on both tusks, but they are looking beautiful now! A small rib fragment was found against the left tusk. Much more of the tusks remain to be prepared in the fall.

Lab Work

This term in the lab we prepared a number of small bones and continued work on some long bones making the following progress:

The small bones that were prepared included one rib piece about 35 cm long, some bones from the hands (metacarpals), an isolated end section from a long bone, several unknown small bones or bone pieces, and the atlas (first neck vertebra behind the skull). Students sawed off the plaster field jackets, removed matrix, cleaned, and consolidated these bones with butvar.

Right tibia – The side of the tibia that had been exposed before burial and in contact with the left tusk was prepared. This side shows more weathering than the other side and has damage where it was against the tusk.

Right ulna and radius – Preparation of one side of these articulated bones was nearly completed by Rachel Lindstrom over the winter of this year as she was preparing to measure Benny’s long bones for her senior capstone project. Students finished preparing it this spring.

Senior Capstone Project – What Species Is He?

Rachel Lindstrom chose to measure the long bones (leg bones) of our mammoth and compare them to comparable measurements of mammoths identified as Mammuthus primigenius (woolly mammoth) and Mammuthus jeffersonii (Jefferson’s mammoth). Based on teeth measurements made and overall characteristics noted by Jeff Saunders, we think Benny belongs to the latter species. Recognizing the fact that Benny is only one individual and may not represent the average size for his species, Rachel found that his long bone lengths are closer to those of a Jefferson’s mammoth than a woolly mammoth. A Jefferson’s mammoth was larger than a woolly mammoth, and, according to Jeff Saunders, its habitat was open woodland (spruce) in the Great Lakes region of North America.

Dr. David Grimley of the Illinois State Geological Survey notes that terrestrial gastropods (snails), typical of boreal woodlands, and occasional spruce wood have been found in the Peoria Silt (a loess deposit) in uplands and sloping areas adjacent to the floodplains of the Mississippi River in the St. Louis Metro East region (e.g. near Collinsville). The Peoria Silt is the unit that entombed Benny. Early in our project we sifted the Peoria Silt as it was excavated, but found that it is too leached of carbonates to have preserved snails. Based on previous studies of gastropods and ostracodes in the region (Leonard and Frye, 1960; Grimley et al., 2001; Curry and Delorme, 2003), it is envisioned that the Principia campus area would have been an open woodland environment (or parkland-type area), well suited for a Jefferson’s mammoth. During the time of Benny (~17,500 radiocarbon years ago), borealtype woodlands likely occurred in hilly areas along the bluffs, protected ravines and small stream courses, whereas the broad Mississippi-Missouri Valley below (the American Bottoms) more likely consisted of grassland and wetland type vegetation in a shifting braided river environment. More open grasslands may also have occurred in the flatter plains to the north and east of Principia interspersed with areas of woodlands. Climatic reconstructions for the St. Louis region based on ostracode fossils suggest a mean annual temperature about 10 degrees Celcius cooler than today during the last glacial maximum (Curry and Delorme, 2003), with a modern analog occurring in the boreal forests or parkland areas of central or south-central Canada.

Outreach

Visitors

During this term we hosted about 160 visitors including six area school groups ranging from preschool to high school and a few adult groups. We hosted one 5th grade class for a tour and activities that included making plaster casts of mammoth teeth. My students participated in all of our tours as guides explaining what we do in the field and lab and what we have learned about mammoths.

Local News

Channel 4 (KMOV/CBS) News in St. Louis returned May 20th to do a follow-up story on what we had found in the skull. They again shot some footage during the day and returned that night with crew and a satellite dish to do the story live from our Science Center garage where the skull block resides.

Talks

Janis Treworgy gave three talks this winter to about 240 people for the following groups:

  • Jerseyville Historical Society Annual Meeting
  • Madison County Soil and Water Conservation District Annual Meeting
  • Illinois State Museum’s Paul Mickey Lecture Series in Archeology and Natural Sciences

-Janis Treworgy

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