First direct evidence of ammonoid ovoviviparity

DWhatley

Kraken
Staff member
Moderator
Joined
Sep 4, 2006
Messages
20,722
Reaction score
1,853
Location
Gainesville, GA
First direct evidence of ammonoid ovoviviparity
Aleksandr A. Mironenko, Mikhail A. Rogov 2015 (subscription)

Ammonoids had high evolutionary rates and diversity throughout their entire history and played an important role in the high-resolution sub-division of the Mesozoic, but much of their palaeobiology remains unclear, including the brooding habitat. We present our study of the first recorded ammonite embryonic shell clusters preserved with calcified embryonic aptychi in situ within the body chambers of mature macroconch shells of the Early Aptian (Early Cretaceous) ammonite Sinzovia sazonovae. The following support the idea that the clusters are egg masses, which developed inside ammonite body chambers: the absence of post-embryonic shells and any other fossils in these clusters, the presence of the aptychi in all embryonic shell apertures and peculiarities of adult shells preservation. These facts confirm earlier speculations that at least some ammonoids could have been ovoviviparous and that, like many modern cephalopods, they could have reproduced in mass spawning events. The aptychi of ammonite embryonic shells are observed here for the first time, indicating that they were already formed and calcified before hatching. Our results are fully congruent with the peculiar modes of ammonoid evolution: quick recovery after extinctions, distinct evolutionary rates, pronounced sexual dimorphism and the nearly constant size of embryonic shells through ammonoid history. We assume that adaptation to ovoviviparity may be the reason for the presence of these features in all post-Middle Devonian ammonoids.
 

tonmo

Cthulhu
Staff member
Webmaster
Joined
May 30, 2000
Messages
10,024
Reaction score
940
Location
Pennsylvania
Cool! Had to Google it, of course :rolleyes:

Ovoviviparity, ovovivipary, or ovivipary, is a mode of reproduction in animals in which embryos that develop inside eggs remain in the mother's body until they are ready to hatch.
 

DWhatley

Kraken
Staff member
Moderator
Joined
Sep 4, 2006
Messages
20,722
Reaction score
1,853
Location
Gainesville, GA
I wonder if this was translated to English since this statement, "These facts confirm earlier speculations that at least some ammonoids could have been ovoviviparous and that, like many modern cephalopods, they could have reproduced in mass spawning events. " does not make a lot of sense. Extant cephalopods do not keep fertilized eggs internally.
 
Joined
Sep 16, 2005
Messages
4,936
Reaction score
255
Location
Pittsburgh, PA
In reading the preview, it appears that the evidence of ovoviviparity is that all the eggs are of the same developmental stage (if they had been laid in an empty shell, by multiple ammonites then the eggs would have different developmental stages) AND there were no other artifacts in the shell (like fish scales, other shells or plant remains).
 
Joined
Sep 16, 2005
Messages
4,936
Reaction score
255
Location
Pittsburgh, PA
Well, then it would have to be freshly dead, no algae growth, no other debris from the ocean floor - at least that is their stance on this. When I have an extra 48 hours, I am going to spring for the $6 and I will share a synopsis.
 

Members online

Latest Posts

Forum statistics

Threads
20,325
Messages
204,888
Members
8,481
Latest member
SCpetsgo

Monty Awards

TONMOCON IV (2011): Terri
TONMOCON V (2013): Jean
TONMOCON VI (2015): Taollan
TONMOCON VII (2018): ekocak

Top