No this isn't a dolphin vertebra. To aid identification could I ask some questions? Where was it found, could you upload a photo taken from the side? What size is it? (You could put a ruler in the photo if possible). Thank you
I would agree with this being bovine but I am not sure that it is cervical. Cervical vertebra have three foramina in them, a central one for the spinal cord and two either side for the vertebral artery. The transverse processes of cervical vertebra tend to point more forward than on this specimen, hoever the vertebral body is typical for cervical. If you can see a joint facet on the side of the vertebra then it would be the first thoracic.