The Lion (Leo) was known in the New Kingdom
Astronomical Drawings of the New Kingdom: The Northern Constellations
In the tomb of SETI I, the northern portion of the astronomical ceiling the artist depicted the sky as seen looking north and panning from east to west (right to left) going from the Hippopotamus  to the Bull  and the Lion . We know with certainty that the Hippopotamus is our constellation of Draco, and that the Bull (sometimes also a Bull’s Thigh or Leg) is our constellation of Ursa Major (Great Bear/Big Dipper/Plough). But what constellation is the figure of the ‘Lion’?
Fig. III.69 Arrangement of the northern constellations on the astronomical ceiling of Hall K of the tomb of Seti I (cf. Figs III.65b and III.65c). Taken from Neugebauer and Parker, Egyptian Astronomical Texts, Vol. 3 Texts, p.188, Fig. 31, but with bracketed numbers added.
The image below shows the northern portion of the sky, but this time with Draco/Hippopotamus in the western area and the ‘Lion’ in the eastern area. The celestial pole, according to many authorities, is represented by the hand of the HippopPart 1 Part 2 Part 3 Part 4 Part 5otamus figure holding the rope that is linked to the rear of the Bull. This spot was once occupied by Alpha Draconis, the ancient pole star.
Fig. III.71a Mirror image of the northen constellations as given in the tomb of Seti I (cf. Fig. III.69) with the circles (representing stars) connected by heavy lines. Prepared by Biegel, Zur Astrognosie der alten Agypter, Fig. 6a, after p. 36. (numbers 2, 5 and 9 depict the Hippopotamus, Bull and Lion respectively).
The image (below left) depicts the northern portion of the sky on the Circular Zodiac of Denderah. It can be clearly seen that it is the same arrangement as Fig. III.71a above, except that the image has been simply ‘flipped’ round thus having the Lion looking towards the Hippopotamus and not away as in the Denderah Zodiac. It is nonetheless quite obvious that the Lion in Figs. III.69 and Fig. III.71a is the same as that shown in the Denderah Zodiac, and which has long been identified to our constellation of Leo.
The sketch (below right) shows a reconstruction of ancient sky c. 1350 BC with Denderah Zodiac figures superimposed.