Dinosaur dined on cycad seeds, according to articles in Earth Archives 20 February 2017 and Scientific Reports doi:10.1038/srep42778, published online 16 February 2017.
A team of scientists from Argentina, Spain and Portugal have studied the fossil of a dinosaur found in the Los Molles Formation, in Argentina, dated as middle Jurassic (Approx. 170 million years old). The dinosaur has been named Isaberrysaura mollensis and consists of an almost complete skull with vertebrae, ribs, shoulder and pelvic bones. The researchers estimated it to have been 5 – 6 metres (16.4 – 20 ft) long and described it as “of general stegosaurian appearance”.
Within the specimen close to the posterior ribs they found “a mass of permineralised seeds”. The seeds were a mix of large and small seeds. The smaller seeds have yet to be identified, but the larger ones were identified as cycad seeds. These seeds had three layers with the same structure seen in living cycad seeds. Because all three layers were present the animal must have swallowed the seeds whole without chewing, and the process of digestion had not started on them.
In living cycad seeds the outer layer, called the sarcotesta, is fleshy and nutritious, but the middle layer, called the schlerotesta, is hard and indigestible. This ensures that inner parts of the seeds containing the embryonic plants are passed through the animal’s digestive tract without being broken down.
Living cycads contain toxic chemicals, but the researchers suggested that microbes living in the animal’s gut could have produced an enzyme that broke down the toxic chemicals, and therefore dinosaurs would have acted as seed dispersers for cycads. They also noted that some present day large animals such as elephants and peccaries swallow whole cycad seeds, complete with the fleshy sarcotesta, without chewing.
The dinosaur had teeth similar to that of living iguanas, which eat a mix of animal and plant foods, but the dinosaur stomach contents were “composed entirely of seeds, with no evidence of animal remains.”
Editorial Comment: The question raised by researchers about how creatures could avoid the toxicity of cycad seeds is interesting, as the seeds of living cycads do contain a toxic chemical named cycasin. But as other researchers have noted, cycad seeds are well structured for being dispersed by large animals who swallow the seeds whole, digesting the fleshy sarcotesta yet allowing the hard schlerotesta and inner kernel of the seed to pass through intact, then get deposited in the animal’s droppings. Furthermore the fleshy sarcotesta has very low levels of cycasin so it can be digested without poisoning the animal if swallowed whole without crushing inner parts of the seeds. (J Chem Ecol. 2014 doi: 10.1007/s10886-014-0490-5) Also, according to the Australian research organisation CSIRO, “Horticulturalists have learned that cycad germination rates are greatly improved when the schlerotesta is abraded by a knife or file and when the seeds are soaked in concentrated acid, mimicking the passage of a seed through the digestive tract.” (Cycad Newsletter, 30 (1) March 2007, page 7)
This kind of seed dispersal is well known for other plants, involving other large animals and birds swallowing the seeds whole and passing them out in their droppings. The CSIRO article also comments that dinosaurs such as prosauropods, sauropods and stegosaurs might have used their teeth like rakes to collect seeds whole. Some dinosaurs have also been found with stomach stones, i.e. stones swallowed whole that help grind up tough food. These would also abrade any very hard seeds, further facilitating the seeds for germination when they have passed through a dino digestive tract.
The researchers’ suggestion that the dinosaurs also had enzymes that broke down any toxins from the seeds is possible. We would like to add another suggestion: the seeds were not toxic when they were originally designed to attract animals to eat them and gain benefit, yet pass the reproductive part of the seed through the digestive system without destroying it. Originally, the plant may have just made enough cycasin to act as a warning signal to prevent browsers completely destroying the plants or seeds, but not poison them. A very clever mechanism to benefit all concerned in God’s original good world. The high level of the toxic chemical cycasin in present day cycad leaves and seeds is therefore the result of degeneration of the plant.
Finally, it is no surprise to us that a dinosaur would only eat plants, whatever its teeth were like, because in the beginning all animals were created to eat plants. (Genesis 1:30)
Evidence News vol. 17, No. 2
7 March 2017
Creation Research Australia
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