If you wanted to consult the geologic time scale for when the first vertebrates evolved

Ordovician period

Explanation:

The vertebrate animals are those which are comprised of a backbone or a spinal cord. These organisms started to evolve initially during the time of the Ordovician period, which forms the second contrasting period of the Paleozoic era.

The Ordovician period belongs to the time, about 450 million years back. This period lasted for about 45 million years and a lot of events has taken place during this time. The oldest vertebrate fossils belonging to the Ordovician period are the ostracoderm that includes the jawless and armored fishes.

Thus, the first vertebrate fossils were evolved during the Ordovician period.

a maximum–minimum thermometer. the scales are fahrenheit on the inside of the u and celsius on the outside. the current temperature is 23 degrees celsius, the maximum recorded is 25, and the minimum is 15, both read from the base of the small markers in each arm of the u tube. the bulbs are hidden by a plastic housing.

six's thermometer is a registering thermometer which can record the maximum and minimum temperatures reached over a period of time, for example 24 hours. it is used to record the extremes of temperature at a location, for instance in meteorology and horticulture. it was invented by a british scientist james six, born in canterbury, in 1780; [1] the same basic design remains in use.

it is also commonly known as a maximum–minimum, minimum–maximum, maxima–minima or minima–maxima thermometer, of which it is the earliest practical design.

the thermometer indicates the current temperature, and the highest and lowest temperatures since last reset.