notochord
noun
no·to·chord ˈnō-tə-ˌkȯrd 
: a longitudinal flexible rod of cells that in the lowest chordates (such as a lancelet or a lamprey) and in the embryos of the higher vertebrates forms the supporting axis of the body
notochordal
ˌnō-tə-ˈkȯr-dᵊl
adjective 
Example Sentences
Recent Examples on the Web The tailfin and notochord — basically the sturgeon’s spine — is pulled out. 
oregonlive, 25 Aug. 2021 But that streak is important—it’s a notochord, or a precursor of our spinal column that marks Pikaia as one of the earliest relatives of vertebrates. Riley Black, Smithsonian Magazine, 10 Dec. 2020 But several fossils revealed that the band bore the hallmark traits of a notochord, the rubbery tube surrounding some primitive vertebrates’ spinal cords. Michael Greshko, National Geographic, 16 Mar. 2016 Instead what’s called a notochord, a flexible rod of tissue, extends along hagfish backs. Susan Milius, WIRED, 2 Mar. 2011
oregonlive, 25 Aug. 2021 But that streak is important—it’s a notochord, or a precursor of our spinal column that marks Pikaia as one of the earliest relatives of vertebrates. Riley Black, Smithsonian Magazine, 10 Dec. 2020 But several fossils revealed that the band bore the hallmark traits of a notochord, the rubbery tube surrounding some primitive vertebrates’ spinal cords. Michael Greshko, National Geographic, 16 Mar. 2016 Instead what’s called a notochord, a flexible rod of tissue, extends along hagfish backs. Susan Milius, WIRED, 2 Mar. 2011 Word History
Etymology
Greek nōton, nōtos back + Latin chorda cord — more at cord
First Known Use
1848, in the meaning defined above
Medical Definition
notochord
noun
no·to·chord ˈnōt-ə-ˌkȯ(ə)rd
: a longitudinal flexible rod of cells that in the lowest chordates (as a lancelet or a lamprey) and in the embryos of the higher vertebrates forms the supporting axis of the body, that is almost obliterated in the adult of the higher vertebrates as the bodies of the vertebrae develop, and that arises as an outgrowth from the dorsal lip of the blastopore extending forward between epiblast and hypoblast in the middorsal line