Phylogenetics Lab: Character Descriptions 1) Osseous Auditory Canal. 0= absent, 1= present. Does the organism have a bony auditory canal? This will look like a hole or opening in the skull behind the jaw and cheekbones. This bony canal serves to amplify sound. To see this character, open the lateral view of the cranium of each taxon. Osseous Auditory Canal Phylogenetics- Character Descriptions: Page 1 of 8
2) Frontal Sinus. 0=absent, 1= present. The frontal sinuses are a pair of cavities located above the orbits in the frontal bone of the cranium. They function to produce mucus and open to the nasal passage. Because this character cannot be viewed we have coded it for you. 3) Orbits, 0=facing laterally or anterolaterally, 1= facing more anteriorly. The orbits are the depressions in the skull where the eyes are located. Facing laterally means that the eyes would point toward the sides. This provides for a larger visual field, but does not allow for good depth perception because the visual fields of the two eyes do not overlap. Facing more anteriorly means that the eyes face forward, allowing for better stereoscopic vision. To determine whether each taxon has laterally or anteriorly oriented orbits look at the cranium in the ventral and lateral views. Orbits facing forward (anteriorly) Orbits in the skull of Solenodon facing laterally Phylogenetics- Character Descriptions: Page 2 of 8
4) Post- orbital Plate. 0=absent or incomplete, 1=present, complete. The post- orbital plate is the bony surface that would lie behind an eye. These fully enclosed eye- sockets provide added protection for the eyes. This may reflect an increased importance of vision in diurnal animals. To view this anatomical character, open the ventral view of the cranium for each taxon. 5) Pre- molars. 0=three upper and lower premolars present, 1=two upper and lower premolars present. The upper teeth can be seen in the caudal view of the cranium while the lower teeth can be seen in the occlusal view of the mandible. You may also click on mandibular or maxillary dentition. Note: the marmoset has only two molars. Phylogenetics- Character Descriptions: Page 3 of 8
6) Femoral condyles. 0=symmetrical, 1=markedly assymetrical (the medial condyle is larger). The femur is the large thigh bone. The femoral condyles are the bumps on the end of the bone that form the joint with your lower leg bones. This asymmetry is advantageous for walking on the ground. To view these bones select the dorsal and distal views of the femur. Note: the gibbon has been coded for you because this is a difficult distinction. Do not use this specimen as a guide for symmetry or asymmetry. Phylogenetics- Character Descriptions: Page 4 of 8
7) Pelvis. 0=acetabular fossa is smaller than obturator foramen, 1= acetabular fossa same size as obturator foramen. The pelvis is the bony structure that connects the end of the spine to the top of the legs. A fossa is a depression or hollow in a bone. The acetabular fossa is the depression in the pelvis, which forms the joint with the top of the thigh bone. A foramen is an opening in a bone which allows nerves and muscle fibers to pass through, connecting one part of a body with another. The obturator foramen allows for the passage of the obturator nerve (among other things). The increased size of the acetabular fossa reflects a similar increase in size of the top of the thigh bone and a reliance on more upright walking. To look at this character open the lateral view of the os coxa. You will only be able to assess this for some of the taxa the others have been coded for you. Phylogenetics- Character Descriptions: Page 5 of 8
8) Rhinarium and upper lip. 0=rhinarium moist and upper lip is split, 1= rhinarium dry and upper lip is not or is only partially split. Most mammals possess this nose pad. Rhinarium 9) Tapetum lucidum. 0= present, 1=absent. The tapetum lucidum is a layer of tissue in the eye of many vertebrate animals. It reflects light back through the retina allowing for more light to be available to photoreceptors. This helps with vision in low light (especially in nocturnal animals). When light shines on the eye of an animal that has a tapetum lucidum, the pupil appears to glow. Phylogenetics- Character Descriptions: Page 6 of 8
10) Pre- maxillary suture. 0 = present in adulthood, 1 = absent in adulthood. The diagram below shows the normal development of the palate with the fusion of the premaxilla with the maxillary processes creating the premaxillary suture, which eventually disappears during human development. If this fusion does not occur a cleft lip/palate may result. 11) Toothcomb. 0=absent, 1=present. A toothcomb is a dental structure found in some mammals, which is made up of the front teeth (the four incisors) and is used for grooming. Phylogenetics- Character Descriptions: Page 7 of 8
12) Size of the third digit on the foot (middle toe). 0 = largest, 1 = not largest (fourth digit is largest) Phylogenetics- Character Descriptions: Page 8 of 8