Midden Analysis

Introduction

Over a few months, the midden from the site designated AZM has been analyzed by individuals in the Archaeozoology course. Without the context or background information on the site the shell and bones’ forms, as opposed to the site’s location or date, are the only way to identify and quantify them from the rest. With this information, it is possible to surmise from where this midden site could have been located. As one of those individuals, I received a bag labelled AZM-3. This bag contains flaked stone, mollusc shells, including species from gastropods and bivalves, various species of boney fish (Osteichthyes), bird specimens, including moa, and examples of mammals. Because history tells us that large species of moa did not live alongside mammals this creates more of a mixture of dating. In this report, I will explain how I identified the various elements of organisms within the midden sample as well as actively identify specimens and quantify the elements found. This information will let me work out percentages for each class of specimens, and work down to the identifiable elements from each taxonomic group. In turn, this will lead me to derive the most likely period in which the midden was ‘built’, how the material was procured, whether by nature or by humans, where in New Zealand it would have existed and what environments would have been present. With this information, it would be possible to find possible site matches to which future archaeologists could return and complete more research on the area.

Material & Methods

After being presented with bag AZM the task was to the processes of identification and quantification. To begin with, the contents were emptied of the bag into a large white tray with another on the side and began to space out the specimens before I started grouping them by overall class, flaked stone, shell, and bones from fishes, birds, and mammals. Because a majority of the specimens in the bag appeared to be shellfish I had them in the second large white tray and worked to separate them between Gastropods and Bivalve molluscs. Full specimens and specimens with distinguishing features were divided into the smallest taxonomic group possible by comparing the midden specimens with pictures in the University of Otago’s resource collection and the books: New Zealand Seashell Visual Guide from 2010 by Raven, J. and Bracegirdle, S., and Which Seashell? by Crowe A. in 1999, and then placed into labelled bags. Because there were broken fragments of the shell with no distinguishing element that could not be specifically identified as one particular species, family, or class these were grouped in their bags and weighed, instead of counting out the NISP (number of identified specimens). From the shells that could be identified and the fragments with visible hinges, the element used for the quantification in the bivalves, or the apexes, the element used for the gastropods, the MNE (minimum number of elements) was counted, and once the tables were filled, the MNI (minimum number of individuals) was calculated.

For the fish, the pieces that could be identified as being examples of the ‘Big 5’ portions of the skull, which are the: Articular, Dentury, Maxilla, Premaxilla, and Quadrate were placed in individual bags and labelled as such. They were identified using the illustrations of identified and sided pieces from A Guide to the Identification of Fish Remains… by Leach, 1997 and the previously identified species in Fishbone collection in The University of Otago’s Lab specimens were sided from the shapes and positions of the landmark portions, also the easiest method of identifying the species. Other pieces grouped in individual specimen bags were vertebrae and ribs, without identifying markers of species and the least specific as the bags with ‘non-distinguishing cranium fragments’ and ‘fish bone fragments’, neither of which could be readily identified, much less named through species.

The bird and mammalian bones were identified by the morphology and the landmark fragments. The mammal specimens included vertebrae, ribs, pieces of long bone, and several non-diagnostic pieces. The fewer bird specimens included mostly landmark pieces, such as vertebrae, and several bones from the hind limbs, but most species couldn’t be identified.

Lastly, there was also unidentifiable burnt material and flakes of various types of stone, including flint and obsidian. These specimens were easy to differentiate from the other pieces of the midden collection because of their textures and shapes.

Because the second main purpose of the report is to quantify what has been found, the NISP, MNE, and MNI must be involved. NISP stands for several identified species, meaning the total number of separate pieces. MNE, or the minimum number of elements, is based on the number of specific bone fragments, with which one could identify the bone and the side. MNI is the minimum number of individuals that can be identified based on the number of parts of the landmark portions of bone MNE. The reason for doing this counting is to get an accurate reading of how much fishing is occurring in an area and therefore future researchers would be able to interpret the ecological differentiation over time. One fish may have been broken into hundreds of bone fragments, but when the data is interpreted it would have less of a far-reaching environmental effect than if fifty fish were broken into a few larger fragments.

Results

The species of fish which were identified within the midden include Barracouta [Thyrsites atun], Frostfish [Lepidopus], Gemfish [Rexea solandri], Grouper [Polyprion oxgeneious], Ling [Genypterus blacodes], Red Cod [Pseudophycis bachus], and Rock Cod [Lotella rhacinus], as well as species that I was unable to identify. The graph below shows the breakdown between species and the specimens found.

Fish

Bivalves

The species of Mollusks included both Gastropods and Bivalves. (little shells are bycatch)

Birds and Mammals

Discussion – Interpretation

Based on the pieces that were found in the mystery midden it is likely that the site was coastal.

Conclusion

With a sample size as small as what I’ve examined, however, these conclusions are not definitive. But, I have achieved the purpose of this report, which was to identify and quantify the species present in the small assemblage I was given. The data that I have provided in this report can be further utilized in the future after combining with the other data sets from the same site and the ecological and archaeological contexts to come up with substantiated conclusions.