Preparing Your Assemblage

  • 1. Organize bags of animal bone by provenience.
  • 2. Use an inventory of these bags and their provenience as a checklist.
  • 3. Inspect the bones contained in several bags before beginning your analysis.
  • 4. Use one or more metal or plastic trays to hold the bones of a single bag while analyzing them. Be sure to keep the provenience information with the bones by placing labels on or in each tray.
  • 5. Use a denture brush and dull-tipped dental picks to remove dirt as needed.
  • 6. Use a 10X magnification loop to inspect the bone as needed.
  • 7. Sort bones from a single bag by laying them out with the most similar ones together.
  • 8. Remove any non-bone materials such as rocks, twigs, and fragments of ceramic; bag these separately as “non-bone”; be sure to preserve the provenience information.
  • 9. Set up a sandbox for bone mending.
  • 10. Inspect the bones for fresh breaks and make any mends that are possible

    Sorting Bone from Non-Bone

  • Bone vs. Stone—Bone sticks to the tongue. Stone produces a sharp sound when dropped on a table.
  • Bone vs. Ceramic—Bone sticks to the tongue. A thumbnail can scratch calcined bone. Most ceramics will not stick to the tongue or be easily scratched.
  • Bone vs. Plant—Bone usually does not float. Plant material will compress if pushed on with a thumbnail.

    Making Identifications with Certainty

  • 1. Reliable data is what you know, not what you think. Always check your intuition against a reliable source. No matter how many deer femurs you have seen in your lifetime, you should always compare the bone you think is a deer femur to an actual deer femur, or a scale illustration of a one. Don’t get sloppy just to save time.
  • 2. Exclusion is as important as inclusion. Sometimes figuring out what your bone is not is the simplest way to increase your certainty as to what it actually is. Check species lists for the other sites in the area. Check the geographic distributions of species in the state.
  • 3. If you are going to make an unusual identification, you need to be 100 percent certain. Don’t identify an Arizona gray squirrel tibia in an assemblage from New York unless you are positive it is an Arizona gray squirrel and not an eastern gray squirrel.
  • 4. Ignore identifications made by others. Field bags and field notes are filled with the intuitions of others, and often these notes can lead you astray. I once spent days looking for a sheep skull that a field crew kept asking about only to discover that the pig cranium I had already identified had been mistakenly identified by the crew.
  • 5. Don’t make an identification just to avoid admitting you are not sure what it is. Every assemblage has its unidentifiables.

    Identifying Antler and Horn Fragments

  • Antler—very wood-like or bark-like exterior surface and very dense outer cortex and inner spongy bone, no interior cavity
  • Horn—very dense exterior and interior surfaces are porous with holes penetrating from the exterior surface into the interior

    Characteristics of Vertebrae by Taxonomic Class

  • Mammal—large size with complex shape, large central foramen, flat articular surfaces
  • Fish—roundish solid centrum with little or no central foramen
  • Bird—complex shape with small central foramen, saddle-shaped articulations, rear-facing spines on lateral surfaces, fusion of vertebrae
  • Reptile—small central foramen, roundish central body with a ball-like projection at one end and a depressed articular surface at the other (turtles have two lobes on central body)
  • Amphibian—small central foramen, oval-ish central body with relatively flat articular surfaces, large lateral projections

    Differentiating Mammal Vertebrae

  • Cervical—small centrum; overall ring-like shape; three foramina
  • Thoracic—larger centrum; large spinous process
  • Lumbar—largest centrum; short spinous process; large transverse processes
  • Sacral—fuse to form sacrum
  • Caudal—small central foramen or no foramen; small transverse processes; may appear star-shaped in cross-section

    Differentiating Fish Vertebrae

  • Cervical—no neural spine
  • Thoracic—neural spine extends up from central body and points toward tail
  • Precaudal—neural spine plus transverse processes extending out to sides
  • Caudal—neural spine plus haemal spine extending downward
  • Penultimate—only a short neural spine
  • Ultimate—no spines, support for tail fin present

    Differentiating Bird Vertebrae

  • Cervical—small centrum; three foramina; rear-facing thin bone projections (hypapophyses)
  • Thoracic—larger centrum; large neural arch and spinous process; may be fused together
  • Lumbar—fused vertebrae; also fused to sacral vertebrae and pelvis
  • Sacral—fused to pelvis as part of synsacrum
  • Caudal—small centrum with spinous and transverse processes
  • Pygostyle—vertebral body with finlike projection

    Identifying Fragments of Vertebra

  • Mammal—tend to break into complex shapes; fragments of centrum are porous; fragments of spinous and transverse processes resemble ribs but are thinner
  • Fish—tend to separate into round central bodies and long, thin spines; the bodies resemble spools with depressed ends; the spines resemble sewing needles with a triangular end at the attachment to the centrum
  • Bird—vertebra are robust and often fused together or to other bones, making breakage difficult
  • Reptiles—vertebra are small and robust, making breakage difficult
  • Amphibians—vertebra are small and robust, making breakage difficult

    Identifying Rib Fragments

  • Mammal—squarish in cross-section; inner spongy bone is more organized and less dense than in long bones
  • Fish—very long, thin, and curved with transparent to translucent character
  • Bird—flat and some are forked near mid-shaft for the uncinate process

    Identifying Fragments of Pelvic Girdle

  • Mammal—complex shape with thin to thick outer cortex and disorganized spongy bone throughout the interior
  • Bird—fragments that do break off tend to be very thin; otherwise the fusion makes the bone resistant to breakage
  • Reptile—density of the acetabulum and ilium makes these the most common fragments that are still identifiable
  • Amphibian—density of the acetabulum and ilium makes these the most common fragments that are still identifiable

    Characteristics of Pelves by Taxonomic Class

  • Mammal—deep acetabulum and large obturator foramen
  • Fish—located near cranium; has fin support structures; shaped like a wishbone
  • Bird—fused together to form synsacrum; three foramina form diagnostic pattern
  • Reptile—very shallow acetabulum, except those with large obturator foramina; turtle and tortoise pelves resemble a party mask
  • Amphibian—ilium tends to be the most prominent component of the pelvis

    Identifying Fragments of Shoulder Girdles

  • Mammal—large fragments of thin and flat bone, with no clear interior surface, are usually fragments of mammal scapulae
  • Fish—resemble cranial fragments
  • Bird—scapula fragments resemble rib fragments without uncinate process; coracoids break below proximal articulation, leaving blade fragments that are relatively flat but often with shallow depressions or raised lines
  • Reptile and Amphibian—small size and density makes them resistant to breakage

    Characteristics of Shoulder Girdles by Taxonomic Class

  • Mammal—triangular-shaped scapulae; no coracoids
  • Fish—no scapulae; do have coracoids and clavicles as a complex of fused bones just behind the cranium
  • Bird—scapulae are rib-like in appearance; coracoids are hooked at one end; clavicles are fused to form furcula
  • Reptile—shoulder girdle resembles pelvic girdle but with longer and thinner elements
  • Amphibian—shoulder girdle resembles pelvic girdle but with longer and thinner elements

    Identifying Upper Limb Elements

  • Humerus—proximal articulation is convex (rounded) to form shoulder
  • Ulna and Radio-ulna—proximal articulation is concave (cupped) to form elbow
  • Radius—proximal articulation is relatively flat in profile but relatively circular in plan

    Identifying Upper Limb Fragments of Mammals

  • Humerus—shaft is a twisted cylinder; proximal end is a round knob; distal end is complex with the shaft dividing into two parts just before the articulation
  • Ulna—proximal end is a hook; shaft is relatively thin but is almost entirely hard cortex; distal end tapers to a point
  • Radius—proximal end is flat with a slight depression and round to oval in shape; shaft is often D-shaped in cross-section; distal end flares out

    Identifying Upper Limb Fragments of Birds

  • Humerus—proximal articulation is rounded and contains a diagnostic fossa and/or crest; distal articulation resembles a clenched fist
  • Ulna—shaft is relatively round in cross-section; may have a column of raised quill knobs along shaft; proximal articulation is sloped; distal articulation is W-shaped
  • Radius—shaft is relatively round in cross-section; proximal articulation is roundish with a small facet just below it
  • Carpometacarpus—very dense and complex-shaped bone; proximal articulation resembles a pulley; shaft is split in two; distal articulation may have stepped appearance

    Identifying Upper Limb Fragments of Reptiles

  • All are relatively paddle-shaped with a dense outer cortex. Articular ends are relatively shapeless when compared to those of mammals.

    Identifying Upper Limb Fragments of Amphibians

  • Humerus—proximal shaft has a crest but otherwise has a tubelike appearance and some curvature; distal end is rounded and ball-shaped
  • Radio-ulna—proximal end is concave, and shaft is clearly two shafts fused together; distal end is tubelike but two tubes fused together

    Characteristics of Upper Limbs by Taxonomic Class

  • Mammal—proximal humerus has a rounded knob; proximal ulna has a hook; radius is D-shaped in cross-section
  • Bird—proximal humerus is rounded; distal humerus resembles a clenched fist; radius and ulna are both long and thin; carpometacarpus has a pulley on proximal end and a stepped distal end
  • Reptile—humerus, radius, and ulna are all globular and somewhat paddle-shaped
  • Amphibian—humerus has a rounded distal articulation; radio-ulna is concave at the proximal articulation and fans out from there with two shafts fused together

    Identifying Lower Limb Fragments of Mammals

  • Femur—shaft is very round in cross-section; proximal end has projections known as trochanters; distal end has two large, rounded condyles
  • Tibia—proximal shaft is triangular in cross-section; distal shaft is D-shaped in cross-section; proximal end has two articular surfaces separated by a small ridge; distal articular end has a projection that is positioned medially
  • Fibula—shaft is long and relatively thin and sometimes is fused to the lateral shaft of the tibia

    Identifying Lower Limb Fragments of Birds

  • Femur—resembles mammal femur but has much thinner walls and is lighter in weight
  • Tibiotarsus—proximal articulation is very angular; distal shaft has a shallow canal running down it; distal articulation resembles that of a femur but with less-prominent condyles
  • Tarsometatarsus—distal end has three-pronged shape or three trochleas; proximal articulation resembles that of a mammal tibia but has two foramina, one on the medial and one lateral side of the anterior shaft surface

    Identifying Lower Limb Fragments of Reptiles

  • All are relatively paddle-shaped with a dense outer cortex. Articular ends are relatively shapeless when compared to mammals.

    Identifying Lower Limb Fragments of Amphibians

  • Femur—long and thin with no clear features
  • Tibiofibula—resembles a long, thin, and compact X shape with a depression or foramen at the center

    Characteristics of Lower Limbs by Taxonomic Class

  • Mammal—femur has two large projections at each end; tibia is triangular at proximal end and D-shaped at distal end
  • Bird—femur resembles that of a mammal but with less distinctive shape; distal end of tibiotarsus can be mistaken for a femur, but the proximal end is very tibia-like; tarsometatarsus has complex three-pronged shape to distal articulation
  • Reptile—femur, tibia, and fibula are all somewhat paddle-shaped
  • Amphibian—femur and tibiofibula are long and thin with few features

    Identifying Metacarpal and Metatarsal Fragments of Ungulates

  • Both have a very dense outer cortex with little interior spongy bone. Interior may show remnants of the fusion of two bones together; this is also sometimes evident on the exterior of the bone.
  • Metacarpals—proximal articulation is D-shaped
  • Metatarsals—proximal articulation is square

    Characteristics of Mammal Metapodials

  • Carpals—often resemble small rocks, but have many smooth articular surfaces in between rough surfaces; usually smaller than tarsals
  • Tarsals—larger size and more complex shape makes them easier to identify than carpals
  • Metacarpals and Metatarsals—distal end has knob shape or pulley shape
  • Phalanges—proximal end is concave; distal end is convex; a small shaft is in between

    Body Size Classes

    Birds

  • Tiny—finch or sparrow (<50 grams or 1.76 ounces)
  • Small—thrush (50–100 g or 1.76-3.53 oz)
  • Medium—pigeon (100–400 g or 3.53-14.11 oz)
  • Large—chicken (400-3000 g or 14.11-105.82 oz)
  • Very large—goose (>3 kilograms or 6.6 pounds)

    Mammals

  • Size 1 or Small Mammal—rabbit (< 50 pounds or 22.68 kilograms)
  • Size 2 or Medium Mammal—pig (50–250 lbs or 22.68-113.40 kg)
  • Size 3 or Medium-Large Mammal—deer (250–750 lbs or 113.40-340.19 kg)
  • Size 4 or Large Mammal—cow (750–2000 lbs or 340.19-907.18 kg)
  • Size 5 or Very Large Mammal—elephant (> 2000 lbs or 907.18 kg)