Their skulls show how strange and diverse frogs can be. The last comprehensive study of frog skulls was published in Since then, scientists have doubled the number of described frog species, updated our understanding of their evolutionary relationships and developed new analytical techniques with the help of CT scanning.
This enabled Paluh to use 36 landmarks on frog skulls, scanned and digitized as part of the National Science Foundation-funded oVert project, to analyze and compare shapes across the frog tree of life. Not only do hyperossification and bizarre skull shapes tend to appear together, Paluh found, but they are often associated with frogs that eat either very large prey or use their heads for defense.
Frogs that eat other vertebrates — birds, reptiles, other frogs and mice — often have giant, roomy skulls, with a jaw joint near the back. This gives them a bigger gape with which to scoop up their prey, Paluh said, referencing Pacman frogs as one example.
Other frogs use their heads to plug the entrance of their burrows as protection from predators. They cannot be distinguished from dermal bone, since they differ only in embryonic origin.
The neurocranium bones are painted black on the demonstration wolf and cat skulls. What group of bones surrounds the opening for the spinal cord foramen magnum? W hat group of bones has holes for the cranial nerves? What group of bones forms the back of the box? W hat group of bones forms the bottom and sides of the box? The front of the box is the perpendicular bone dividing the nostrils. What is it called? On either side, in the nostrils, is a complex of thin bones looking like swirls of flaky pastry.
What are they called? What happens with the original top of the box? Draw a stylized rectangular brain box and label the parts of the neurocranium. The splanchnocranium consists of the gill arches and their derivatives. The gill arches serve to support the gills and offer a site for respiratory muscle attachment.
The original branchial skeleton of cartilage came from neural crest cells. Splanchnocranium of a cartilaginous dogfish and salamander. The ossifications of the splanchnocranium of the teleost fishes cannot be readily identified on the wolf skull since they are either the framework for subsequent dermal tooth-bearing bones, or have moved from their association with the jaws to form the ear bones: quadrate incus , articular malleus and hyomandibular columella or stapes.
Look at the alligator and identify the quadrate and articular bones. In mammals, gill arches also form the elements of the larynx hyoid bone, thyroid and cricoid cartilages. See page The original dermal scales or armour of Ostracoderms sink down, attach to the neurocranium and are ossified to form dermal bones.
These are from dermatome epimere mesoderm. The dermatocranium forms most of the skull and functions as a protective shield for the brain. See the dermal armour of Amia , the bowfin, which sits on the cartilaginous neurocranium. In other animal groups the cartilage disappears and when you look down on the skull you are looking at the bones of the dermatocranium. The dermatocranium contributions to the mammal skull that we wish to learn are all those bones that are labeled on the drawing of the wolf skull, plus the dentary bone of the lower jaw.
Identify all of these dermal bones on the wolf skull and learn them. These bones are grouped as the facial upper jaw, nose , v ault front of skull , orbital around eyes , temporal side of skull , palatal roof of mouth and m andibular lower jaw series. There are skulls of an.
Using the drawings and the skulls provided, identify the dermal bones in each skull. Count the total number of dermal bones paired X2 and unpaired X1 in each species. Please use only the drawings in this lab guide for the count.
Note that one pair of bones on one of the drawings is from the splanchnocranium and should not be counted. If any bone is not listed as neurocranium or splanchnocranium on page 39, it is dermal in origin. Number of dermal bones in Amia skull:. Number of dermal bones in the alligator skull:. Number of dermal bones in wolf skull:. Use the space below to draw the paired wolf dentary bones. Bones of the skull and their origins. The bones we will concentrate on in this lab are listed here.
Neurocranium Chondrocranium is from neural crest cells and mesodermal mesenchyme. It can remain catrilage or become replacement bone. We will study three groups of bones the Occipitals, the Sphenoids and the Ethmoids. Splanchnocranium comes from neural crest cells and is either cartilage or replacement bone.
The batrachian skull bones may be derived from those of temnospondyls by truncation of the developmental trajectory. The squamosal, quadratojugal, parietal, prefrontal, parasphenoid, palatine, and pterygoid form rudimentary versions of their homologs in temnospondyls. In addition, failure to ossify and early fusion of bone primordia both result in the absence of further bones that were consistently present in Paleozoic tetrapods.
Here, I propose a new hypothesis explaining the observed patterns of bone loss and emargination in a functional context.
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