I found some interesting versions of description about "Neodinosaurs" on an internet site which is converting the reports into gaming statistics. In this case the base data seems to be drawn from any of a number of Living Dinosaur sites, all of which tend to have much the same data. Here are a couple of examples:
Mountain Boomer Max Height: 7ft (2.1 metres)
Max Length: 18 ft (5.5 metres)
Max Weight: 660lb (300 kilos)
Diet: Herbivore
Agressiveness: 1 [inoffensive]
Rarity: Common
Appearance:

Background Info: The Mountain Boomer is a small sized (by dinosaur standards) bipedal dinosaur evolved from a Thescelosaurus-like ornithopod.
Female Mountain Boomers are generally 6 to 7 feet tall while smaller males are usually 3 to 5 feet high. The males have a more vivid coloration than the females.
The Mountain Boomer are found everywhere ... but tend to nest in the more remote mountain regions where they sleep lives in caves or burrows.
Its is extremely fast, swift and agile, easily being able to outrun a human or other predator. Additionally, it has a tremendous leap.
The creatures are shy and reclusive, fleeing as defence.
They have a strange wolf-like howl. [This last can be discounted as a mistaken actual wolf howl]
The "Kangaroo-Lizard Chupacabras" generally falls into the "Male" range of sizes here but some can be larger. The males have red eyes (red irises). The spiny back crest would go all the way down the back in both sexes but it is larger and more prominent on the male.
Later on there is a similar entry for "River Liz",
River LizardMax Height: 3.5 ft (1 metre)[to five feet]
Max Length: 5 ft (1.5 metres)[to 2 meters/ 7 feet long]
Max Weight: 33 lb (15 kg)
Diet: Omnivore, Insectivore
Agressiveness: 1
Rarity: Very common
Appearance:

Background Info: The River Lizards, as they have come to be known, are a genus of small theropod dinosaur. Their exact evolutionary history is not known at the current time, although a veriety of primitive ornithomimosaur similar to Pelecanimimus or Harpymimus is the most widely accepted theory. Other suggestions have been made that they are perhaps descended from a member of the Troodontidae, or Dromaeosauridae families...[Afterwards bogging down in the Taxonomy]
Both of these models can easily be combined into a description of one kind of "Minidinosaur" and the size given for the "River Liz" matches the"Mountain Boomer" male. In fact there is no reason to make the size differences into sex differences rather than growth stages. The "River Liz" head should similarly be shortened and roundish, and the coloration of both being in basically a green background shading to gray in parts like the belly, overlaind by large irregular brown bands or splotches. The back has a sort of a crest on it and there may be hornlike structures on the head. All of this is in agreement with the actual reports. Whereas originally I was unwilling to allow the "Female" sizes indicated here in the reports I saw, they are actually in the reports that way, and so my disallowal was more a matter of opinion than anything else.
Recently, reportsof "Minidinos" in the Southwesten area of the USA have tended to resemble "Dilophosaurus" out of the movie Jurassic Park, or the modern frilled lizards of Australia. since this is a fancy of the filmmakers and a misrepresentation of the actual dinosaur named, these sightings are unlikely to be of the animal genus so named, but some could be of actual escaped-exotic-pet lizards (Which were all the rage in Japan a few years back)
There has been a recent rash of soghtings of the "MiniRex" lizards that resembled this in the Four Corners area around Hogsback NM. The reports in general (With or without mentioning the frill) are comparable in scale to the dinosaur comparisons made on the charts below:
-Which is just about comparable for the estimates made for the (Texas) "Mountain Boomers" given above. There is also the possible explanations that "Mountain Boomer" reports in the past have specified large flaps of skin above and below the headead of horizontally, such as can be found in other types of known Iguanid lizards living today. Some lizards have the flaps in both places, like some anole lizards ("Chameleons"):
Then there is the South American "Iguanodon" of Heuvelmans:
SaruMax Height: 9.8 ft (3 metres) [9 ft?]
Max Length: 33 ft (10 metres) [24 ft? As per reports]
Max Weight: 3.5 tons (3.0 metric tonnes)
Diet: Herbivore
Agressiveness: 4
Rarity: Medium
Appearance:

Background Info: The Saru is an bizarre herbivorous dinosaur of which has been subject to an extreme amount of evolutionary adaptability. Surprisingly descended from a sauropod, like the Mokele-Mbembe... This adaptation seems to have occurred in order for the animal to fill the ecological niche of the Iguanodonts and Hardrosaurus which are surprisingly absent ....
Behaviour: A herbivore often seen browsing on mid-height vegetation. The Saru can be aggressive if attacked and can kill small predators but prefers to flee in most circumstances.
It is terrestrial but can swim if need be. It moves very slowly, balancing with its long tail.
--I find it interesting that the native name for this is supposed to be "Saurus". Perhaps in South America the Cryptological counterpart is actually called Lagarto? The term "Big Iguana" or "Biguana" has some adherants, and at least one Cryptozoological site refers to it as a "Giant Basilisk Lizard": it is also what Eberhart refers to as the "Venezuelan Monitor"
Venezuelan Monitor
Unknown LIZARD of South America.
Physical description: Large monitor lizard.
Distribution:Galeras de El Pao, in Guárico and
Cojedes States, Venezuela; near Angel Falls, Bolí-
var State, Venezuela; the Cerro Santa Ana, Penin-
sula de Paraguana, Falcón State, Venezuela.
Significant sightings: A prospector from Cara-
cas told ecologist Léon Croizat in 1972 that a
large lizard resembling a Komodo dragon lived
in the Galeras de El Pao. Herpetologist J. B. Graham saw a large, unknown lizard near the base of the Cerro Santa Ana in 1976 or 1977.
Sources: Silvano Lorenzoni, “More on Extant Dinosaurs,” Pursuit, no. 47 (Summer 1979):
105–109; Silvano Lorenzoni (letter), Pursuit,no. 50 (Spring 1980): 95.
http://www.angelfire.com/bc2/cryptodominion/cryptosaurs.html
Mountain boomer (West Texas NA): A 6 foot tall dinosaur-like animal reported
from areas of western Texas. If it exists, think it is some kind of large,
bipedal lizard, perhaps related to the Trimble County lizard, but more strongly
bipedal.
Colorado "dinosaurs" (Pagosa Springs region of Colorado NA): A woman from
this area claims to have seen many dinosaur in her life. She says that she saw 5
babies once when she was little, and that a local farmer killed a 7 foot tall
one a couple months later. She also claims to have run across a green one in a
local cave, and to have seen one many years later while driving on a road near
that same cave. Personally, I think she needs help, and soon, but anyone is
welcome to follow up on her reports. I'm sure not going to.
Colorado "river lizards" (The area around and islands on the Fountain River
NA): A long-standing local folklore in this region includes things like the
prairie devil and "evil river spirits", and recent reports from a local boy
concurr that there may be something strange living on and around the Fountain.
The boy claims to have watched a greenish coloured lizard with black markings
and a yellow-orange belly running on it's hind legs away from him. Anoter local
took a series of pictures, but they are indistinct and could be easily faked.
However, there is one very good picture, showing a man holding up a 3 foot long
lizard with small front legs and long, strong hindlegs. If that was faked, it
was done with a very good model. My personal opinion is that these are bipedal
lizards, like the mountain boomer but smaller.
Amazonian "duckbills" (Northwestern Amazon SA): This is a case showing how
much wishful thinking can really effect what we find to be "true". For the
longest time, the "duck-billed dinosaurs" were considered to be semi-aquatic,
and generally like giant ducks. Thus, living dinosaur fanatics often talk about
aquatic reptiles being sighted in South America, which just *have* to be
hadrosaurs. It is now well known that, not only were hadrosaurs fully
terrestrial grazers, but they were not even bipeds; facultative bipeds perhaps,
but primarily quadrupedal. Their fingers and toes had thick hoof-like nails on
them, and they probably lived an overall bison-like lifestyle. So, then, what
about these "aquatic reptiles" that are sid to exist in the Amazon? Well, short
of calling all the dino-freaks liars, I'll suggest an enormous species of
basalisk. But that's just being courteous.
http://z15.invisionfree.com/primordialpredators/index.php?showtopic=4
:
http://s15.invisionfree.com/primordialpredators/ar/t140.htm
In this case I think we have a fair assumption that we are dealing with one wide-ranging species of Iguanid lizard, blamed for "Chupacabras" crimes in something like its "Mountain Boomer" form, and in which the tropical form in South America could be larger than the subtropical, drier-climate forms in the US SW and in Northern Argentina. The largest ones are really big (20-30 feet maximum is alleged, half of that is probably much more common and more nearly the maximum of the subtropical form) but can still rear up on their hinder legs to about ten feet tall (also alleged in the first instance I heard as being on record in the USA, but I still doubt that report) The smaller ones are omnivores and insectivores but the larger ones are more often herbivorous (but may also take carrion or else perhaps root around in the stomachs of freshly-killed sheep and cattle, eating out the stomach contents?)