It is not known if these are actually the full growth stage of the "River Liz" or a different, larger species. The most parsimonious arrangement would be that both are the same species (and the same as the Cryptid the Greater Dragon Iguana of Latin America)
This is also by way of another displaced reference in that another internet site is selling certain photos of "Water Monsters" which are obviously showing the backs of large iguana lizards swimming in the water but with the spines sticking up. These are not the same as the photo in the one news story that I cannot locate now, but they are comparable. Here are the photos in question, in black and white and in colour (if anything the spines in the photo I am looking for are even larger and more exaggerated)
One example that has been discussed on this blog is the Lake Mead Monster:
Thursday, February 28, 2013
Lake Mead is the largest reservoir in the United States in maximum water capacity. It is located 24 miles from the Las Vegas Strip southeast of Las Vegas, Nevada, in the states of Nevada, and Arizona. The massive lake is reserved by the Hoover Dam. Lake Mead is 112 miles long, and around 500 feet at greatest depth. It holds roughly 28 million acre-feet of water.
According to legends of this cryptozoological creature, In 1948 a B-29 crashed into the lake on July 21. Jet fuel leaked into the lake and polluted the waters. Although the pollution wasn't bad enough to destroy all the life in the water, crypto hunters say it was enough to cause mutations, along with other human waste pollutants.
Shortly after the crash a man was arrested for dropping off alligators in the fresh water. Why this man did this is unknown. Some speculate he owned these alligators as pets, and as they grew too big he was unable to keep them. The legend goes that these same alligators that are believed to live in the waters today have undergone strange mutations. With plenty of fish to eat, these creatures have grown into massive size.
One scuba diver claims to have sited one during a deep water Dam study. The diver described the creature as being at least 20 feet long. Although the lakes waters are very murky he said it was hard to fully identify the creature, but he was sure it was at least 20 feet long, and looked like a super alligator with fins.
Fisherman have also reported seeing this strange creature, although they attribute the features to be a super Bass. In a news paper article published in the 50's, fisherman claims gave it the nickname "Grandad".
Today people still claim to see these strange creatures in the lake, and the search continues. Perhaps we will find out the truth about this creature soon. After all Lake Mead is estimated to dry up by 2020 according to new studies.
A large reproduction of a Spinyback lake monster is on display at Manly Lake in Death Valley
(it seems that some of these creatures can tolerate saltwater to some degree. They do not eat fish in these lakes, they eat plants on the shore. Probably they do not even drink the water)
Presumably this would be based on the sighting of a bigger one followed by a smaller one, both seen as spiky-backed humps on the surface. (Although such creatures are said to grow up to 20 feet long in some locations, this is probably exaggerated)