A thin, tubelike structure called a siphuncle pumped air ... Early ammonites had simple suture lines traced across their shells, while the sutures on species from the Cretaceous period (145 ...

The central suture line between the two columns of plates in each ambulacral ... Tubercles can be perforate or imperforate and crenulate or smooth: more information on tubercle structure is available.

(Nanowerk Spotlight) Every surgical procedure, from routine appendectomies to complex organ transplants, relies on a technology that has remained fundamentally unchanged for thousands of years: the ...