A rather different Theropod Tuesday entry! What you are looking at here are the remains of the third, fourth, and fifth cervical (neck) vertebrae (backbones) of the theropod Acrocanthosaurus atokensis in right lateral view (in other words, you’re looking at their right side--the head would be toward the right). These are part of specimen SMU 74646/FWMNH 938-9, currently housed at the Fort Worth Museum of Natural History in Fort Worth, Texas. Acrocanthosaurus was a very large theropod (though these vertebrae are from a small individual) that lived during the mid-Cretaceous (c. 115 million years ago) and has been found in Oklahoma, Texas, and Wyoming. It is an earlier relative of the even bigger and later Carcharodontosaurus and Giganotosaurus.
The fifth vertebra is relatively complete; the third and fourth are just the top parts of the vertebrae (called the vertebral arches or neural arches). The tops of the vertebrae are toward the top of the picture and comprise the (neural) spines; the overlapping bits below that are called the zygapophyses (how’s that for a Words With Friends word? Nah, too many letters...).
What’s especially interesting about these vertebrae, and about Acrocanthosaurus in particular, is the little prongs on the front ends of the vertebral spines near their tops. Notice that when the vertebrae are articulated (together in their life positions), as they are in this picture, each prong nests inside a hollow on the back side of the spine of the next vertebra in front! I’ve hypothesized that this slight bit of additional bolstering/stiffening might have helped the neck resist torque when an Acrocanthosaurus latched its mouth onto a prey animal, particularly a prey animal much larger than itself, such as a sauropod. But that hypothesis could stand some testing, if anyone out there is looking for a dinosaurological research project!