Wow, yet another dose of time wasting taxonomic vandalism. Metlapilcoatlus Campbell, Frost and Castoe, 2019 is an illegal junior synonym of Adelynhoserserpenae Hoser, 2012.
Under the rules of the ICZN, the International Code of Zoological Nomenclature the earlier name is the correct one and must be used.
See
Hoser, R. T. 2012. A new genus of Jumping Pitviper from Middle America (Serpentes: Viperidae). Australasian Journal of herpetology 10:33-34. Published 8 April 2012.
Full text available at:
http://www.smuggled.com/Issue-10-33-34.pdf
The pirate taxonomy paper which effectively lifts all key material from the 7 year old Hoser paper (without citing it in any way) can be found published online at
http://herp.mx/pubs/2019-Campbell-et-al-New-Generic-Name-for-Jumping-Pitvipers.pdf?fbclid=IwAR3ismIhqQO841SR0H_elMKGdcExKZH0yzv91B319VEcyI-3FEQDAP4HQRk
Cut and paste the text for the link to work.